+[[chapter_pvecm]]
ifdef::manvolnum[]
pvecm(1)
========
:pve-toplevel:
endif::manvolnum[]
-The {PVE} cluster manager `pvecm` is a tool to create a group of
+The {pve} cluster manager `pvecm` is a tool to create a group of
physical servers. Such a group is called a *cluster*. We use the
http://www.corosync.org[Corosync Cluster Engine] for reliable group
-communication, and such clusters can consist of up to 32 physical nodes
-(probably more, dependent on network latency).
+communication. There's no explicit limit for the number of nodes in a cluster.
+In practice, the actual possible node count may be limited by the host and
+network performance. Currently (2021), there are reports of clusters (using
+high-end enterprise hardware) with over 50 nodes in production.
`pvecm` can be used to create a new cluster, join nodes to a cluster,
-leave the cluster, get status information and do various other cluster
-related tasks. The **P**rox**m**o**x** **C**luster **F**ile **S**ystem (``pmxcfs'')
+leave the cluster, get status information, and do various other cluster-related
+tasks. The **P**rox**m**o**x** **C**luster **F**ile **S**ystem (``pmxcfs'')
is used to transparently distribute the cluster configuration to all cluster
nodes.
Grouping nodes into a cluster has the following advantages:
-* Centralized, web based management
+* Centralized, web-based management
-* Multi-master clusters: each node can do all management task
+* Multi-master clusters: each node can do all management tasks
-* `pmxcfs`: database-driven file system for storing configuration files,
- replicated in real-time on all nodes using `corosync`.
+* Use of `pmxcfs`, a database-driven file system, for storing configuration
+ files, replicated in real-time on all nodes using `corosync`
* Easy migration of virtual machines and containers between physical
hosts
Requirements
------------
-* All nodes must be in the same network as `corosync` uses IP Multicast
- to communicate between nodes (also see
- http://www.corosync.org[Corosync Cluster Engine]). Corosync uses UDP
- ports 5404 and 5405 for cluster communication.
-+
-NOTE: Some switches do not support IP multicast by default and must be
-manually enabled first.
+* All nodes must be able to connect to each other via UDP ports 5405-5412
+ for corosync to work.
-* Date and time have to be synchronized.
+* Date and time must be synchronized.
-* SSH tunnel on TCP port 22 between nodes is used.
+* An SSH tunnel on TCP port 22 between nodes is required.
* If you are interested in High Availability, you need to have at
least three nodes for reliable quorum. All nodes should have the
* We recommend a dedicated NIC for the cluster traffic, especially if
you use shared storage.
-NOTE: It is not possible to mix Proxmox VE 3.x and earlier with
-Proxmox VE 4.0 cluster nodes.
+* The root password of a cluster node is required for adding nodes.
+
+* Online migration of virtual machines is only supported when nodes have CPUs
+ from the same vendor. It might work otherwise, but this is never guaranteed.
+
+NOTE: It is not possible to mix {pve} 3.x and earlier with {pve} 4.X cluster
+nodes.
+
+NOTE: While it's possible to mix {pve} 4.4 and {pve} 5.0 nodes, doing so is
+not supported as a production configuration and should only be done temporarily,
+during an upgrade of the whole cluster from one major version to another.
+
+NOTE: Running a cluster of {pve} 6.x with earlier versions is not possible. The
+cluster protocol (corosync) between {pve} 6.x and earlier versions changed
+fundamentally. The corosync 3 packages for {pve} 5.4 are only intended for the
+upgrade procedure to {pve} 6.0.
Preparing Nodes
---------------
-First, install {PVE} on all nodes. Make sure that each node is
+First, install {pve} on all nodes. Make sure that each node is
installed with the final hostname and IP configuration. Changing the
hostname and IP is not possible after cluster creation.
-Currently the cluster creation has to be done on the console, so you
-need to login via `ssh`.
+While it's common to reference all node names and their IPs in `/etc/hosts` (or
+make their names resolvable through other means), this is not necessary for a
+cluster to work. It may be useful however, as you can then connect from one node
+to another via SSH, using the easier to remember node name (see also
+xref:pvecm_corosync_addresses[Link Address Types]). Note that we always
+recommend referencing nodes by their IP addresses in the cluster configuration.
-Create the Cluster
-------------------
-Login via `ssh` to the first {pve} node. Use a unique name for your cluster.
-This name cannot be changed later.
+[[pvecm_create_cluster]]
+Create a Cluster
+----------------
+
+You can either create a cluster on the console (login via `ssh`), or through
+the API using the {pve} web interface (__Datacenter -> Cluster__).
+
+NOTE: Use a unique name for your cluster. This name cannot be changed later.
+The cluster name follows the same rules as node names.
+
+[[pvecm_cluster_create_via_gui]]
+Create via Web GUI
+~~~~~~~~~~~~~~~~~~
+
+[thumbnail="screenshot/gui-cluster-create.png"]
+
+Under __Datacenter -> Cluster__, click on *Create Cluster*. Enter the cluster
+name and select a network connection from the drop-down list to serve as the
+main cluster network (Link 0). It defaults to the IP resolved via the node's
+hostname.
+
+As of {pve} 6.2, up to 8 fallback links can be added to a cluster. To add a
+redundant link, click the 'Add' button and select a link number and IP address
+from the respective fields. Prior to {pve} 6.2, to add a second link as
+fallback, you can select the 'Advanced' checkbox and choose an additional
+network interface (Link 1, see also xref:pvecm_redundancy[Corosync Redundancy]).
+
+NOTE: Ensure that the network selected for cluster communication is not used for
+any high traffic purposes, like network storage or live-migration.
+While the cluster network itself produces small amounts of data, it is very
+sensitive to latency. Check out full
+xref:pvecm_cluster_network_requirements[cluster network requirements].
- hp1# pvecm create YOUR-CLUSTER-NAME
+[[pvecm_cluster_create_via_cli]]
+Create via the Command Line
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
-CAUTION: The cluster name is used to compute the default multicast
-address. Please use unique cluster names if you run more than one
-cluster inside your network.
+Login via `ssh` to the first {pve} node and run the following command:
-To check the state of your cluster use:
+----
+ hp1# pvecm create CLUSTERNAME
+----
+To check the state of the new cluster use:
+
+----
hp1# pvecm status
+----
+
+Multiple Clusters in the Same Network
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It is possible to create multiple clusters in the same physical or logical
+network. In this case, each cluster must have a unique name to avoid possible
+clashes in the cluster communication stack. Furthermore, this helps avoid human
+confusion by making clusters clearly distinguishable.
+While the bandwidth requirement of a corosync cluster is relatively low, the
+latency of packages and the package per second (PPS) rate is the limiting
+factor. Different clusters in the same network can compete with each other for
+these resources, so it may still make sense to use separate physical network
+infrastructure for bigger clusters.
+
+[[pvecm_join_node_to_cluster]]
Adding Nodes to the Cluster
---------------------------
-Login via `ssh` to the node you want to add.
+CAUTION: All existing configuration in `/etc/pve` is overwritten when joining a
+cluster. In particular, a joining node cannot hold any guests, since guest IDs
+could otherwise conflict, and the node will inherit the cluster's storage
+configuration. To join a node with existing guest, as a workaround, you can
+create a backup of each guest (using `vzdump`) and restore it under a different
+ID after joining. If the node's storage layout differs, you will need to re-add
+the node's storages, and adapt each storage's node restriction to reflect on
+which nodes the storage is actually available.
+
+Join Node to Cluster via GUI
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+[thumbnail="screenshot/gui-cluster-join-information.png"]
+
+Log in to the web interface on an existing cluster node. Under __Datacenter ->
+Cluster__, click the *Join Information* button at the top. Then, click on the
+button *Copy Information*. Alternatively, copy the string from the 'Information'
+field manually.
+
+[thumbnail="screenshot/gui-cluster-join.png"]
+
+Next, log in to the web interface on the node you want to add.
+Under __Datacenter -> Cluster__, click on *Join Cluster*. Fill in the
+'Information' field with the 'Join Information' text you copied earlier.
+Most settings required for joining the cluster will be filled out
+automatically. For security reasons, the cluster password has to be entered
+manually.
+
+NOTE: To enter all required data manually, you can disable the 'Assisted Join'
+checkbox.
+
+After clicking the *Join* button, the cluster join process will start
+immediately. After the node has joined the cluster, its current node certificate
+will be replaced by one signed from the cluster certificate authority (CA).
+This means that the current session will stop working after a few seconds. You
+then might need to force-reload the web interface and log in again with the
+cluster credentials.
+
+Now your node should be visible under __Datacenter -> Cluster__.
- hp2# pvecm add IP-ADDRESS-CLUSTER
+Join Node to Cluster via Command Line
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-For `IP-ADDRESS-CLUSTER` use the IP from an existing cluster node.
+Log in to the node you want to join into an existing cluster via `ssh`.
+
+----
+ # pvecm add IP-ADDRESS-CLUSTER
+----
+
+For `IP-ADDRESS-CLUSTER`, use the IP or hostname of an existing cluster node.
+An IP address is recommended (see xref:pvecm_corosync_addresses[Link Address Types]).
-CAUTION: A new node cannot hold any VMs, because you would get
-conflicts about identical VM IDs. Also, all existing configuration in
-`/etc/pve` is overwritten when you join a new node to the cluster. To
-workaround, use `vzdump` to backup and restore to a different VMID after
-adding the node to the cluster.
-To check the state of cluster:
+To check the state of the cluster use:
+----
# pvecm status
+----
.Cluster status after adding 4 nodes
----
-hp2# pvecm status
+ # pvecm status
+Cluster information
+~~~~~~~~~~~~~~~~~~~
+Name: prod-central
+Config Version: 3
+Transport: knet
+Secure auth: on
+
Quorum information
~~~~~~~~~~~~~~~~~~
-Date: Mon Apr 20 12:30:13 2015
+Date: Tue Sep 14 11:06:47 2021
Quorum provider: corosync_votequorum
Nodes: 4
Node ID: 0x00000001
-Ring ID: 1928
+Ring ID: 1.1a8
Quorate: Yes
Votequorum information
Expected votes: 4
Highest expected: 4
Total votes: 4
-Quorum: 2
+Quorum: 3
Flags: Quorate
Membership information
0x00000004 1 192.168.15.94
----
-If you only want the list of all nodes use:
+If you only want a list of all nodes, use:
+----
# pvecm nodes
+----
.List nodes in a cluster
----
-hp2# pvecm nodes
+ # pvecm nodes
Membership information
~~~~~~~~~~~~~~~~~~~~~~
4 1 hp4
----
-Adding Nodes With Separated Cluster Network
+[[pvecm_adding_nodes_with_separated_cluster_network]]
+Adding Nodes with Separated Cluster Network
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-When adding a node to a cluster with a separated cluster network you need to
-use the 'ringX_addr' parameters to set the nodes address on those networks:
+When adding a node to a cluster with a separated cluster network, you need to
+use the 'link0' parameter to set the nodes address on that network:
[source,bash]
----
-pvecm add IP-ADDRESS-CLUSTER -ring0_addr IP-ADDRESS-RING0
+# pvecm add IP-ADDRESS-CLUSTER --link0 LOCAL-IP-ADDRESS-LINK0
----
-If you want to use the Redundant Ring Protocol you will also want to pass the
-'ring1_addr' parameter.
+If you want to use the built-in xref:pvecm_redundancy[redundancy] of the
+Kronosnet transport layer, also use the 'link1' parameter.
+Using the GUI, you can select the correct interface from the corresponding
+'Link X' fields in the *Cluster Join* dialog.
Remove a Cluster Node
---------------------
-CAUTION: Read carefully the procedure before proceeding, as it could
+CAUTION: Read the procedure carefully before proceeding, as it may
not be what you want or need.
-Move all virtual machines from the node. Make sure you have no local
-data or backups you want to keep, or save them accordingly.
-In the following example we will remove the node hp4 from the cluster.
+Move all virtual machines from the node. Ensure that you have made copies of any
+local data or backups that you want to keep. In addition, make sure to remove
+any scheduled replication jobs to the node to be removed.
+
+CAUTION: Failure to remove replication jobs to a node before removing said node
+will result in the replication job becoming irremovable. Especially note that
+replication automatically switches direction if a replicated VM is migrated, so
+by migrating a replicated VM from a node to be deleted, replication jobs will be
+set up to that node automatically.
+
+In the following example, we will remove the node hp4 from the cluster.
Log in to a *different* cluster node (not hp4), and issue a `pvecm nodes`
command to identify the node ID to remove:
----
-hp1# pvecm nodes
+ hp1# pvecm nodes
Membership information
~~~~~~~~~~~~~~~~~~~~~~
----
-At this point you must power off hp4 and
-make sure that it will not power on again (in the network) as it
-is.
+At this point, you must power off hp4 and ensure that it will not power on
+again (in the network) with its current configuration.
-IMPORTANT: As said above, it is critical to power off the node
-*before* removal, and make sure that it will *never* power on again
-(in the existing cluster network) as it is.
-If you power on the node as it is, your cluster will be screwed up and
-it could be difficult to restore a clean cluster state.
+IMPORTANT: As mentioned above, it is critical to power off the node
+*before* removal, and make sure that it will *not* power on again
+(in the existing cluster network) with its current configuration.
+If you power on the node as it is, the cluster could end up broken,
+and it could be difficult to restore it to a functioning state.
After powering off the node hp4, we can safely remove it from the cluster.
+----
hp1# pvecm delnode hp4
+ Killing node 4
+----
-If the operation succeeds no output is returned, just check the node
-list again with `pvecm nodes` or `pvecm status`. You should see
-something like:
+NOTE: At this point, it is possible that you will receive an error message
+stating `Could not kill node (error = CS_ERR_NOT_EXIST)`. This does not
+signify an actual failure in the deletion of the node, but rather a failure in
+corosync trying to kill an offline node. Thus, it can be safely ignored.
+
+Use `pvecm nodes` or `pvecm status` to check the node list again. It should
+look something like:
----
hp1# pvecm status
-Quorum information
-~~~~~~~~~~~~~~~~~~
-Date: Mon Apr 20 12:44:28 2015
-Quorum provider: corosync_votequorum
-Nodes: 3
-Node ID: 0x00000001
-Ring ID: 1992
-Quorate: Yes
+...
Votequorum information
~~~~~~~~~~~~~~~~~~~~~~
Expected votes: 3
Highest expected: 3
Total votes: 3
-Quorum: 3
+Quorum: 2
Flags: Quorate
Membership information
0x00000003 1 192.168.15.92
----
-If, for whatever reason, you want that this server joins the same
-cluster again, you have to
+If, for whatever reason, you want this server to join the same cluster again,
+you have to:
-* reinstall {pve} on it from scratch
+* do a fresh install of {pve} on it,
* then join it, as explained in the previous section.
+The configuration files for the removed node will still reside in
+'/etc/pve/nodes/hp4'. Recover any configuration you still need and remove the
+directory afterwards.
+
+NOTE: After removal of the node, its SSH fingerprint will still reside in the
+'known_hosts' of the other nodes. If you receive an SSH error after rejoining
+a node with the same IP or hostname, run `pvecm updatecerts` once on the
+re-added node to update its fingerprint cluster wide.
+
[[pvecm_separate_node_without_reinstall]]
-Separate A Node Without Reinstalling
+Separate a Node Without Reinstalling
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CAUTION: This is *not* the recommended method, proceed with caution. Use the
-above mentioned method if you're unsure.
+previous method if you're unsure.
You can also separate a node from a cluster without reinstalling it from
-scratch. But after removing the node from the cluster it will still have
-access to the shared storages! This must be resolved before you start removing
+scratch. But after removing the node from the cluster, it will still have
+access to any shared storage. This must be resolved before you start removing
the node from the cluster. A {pve} cluster cannot share the exact same
-storage with another cluster, as storage locking doesn't work over cluster
-boundary. Further, it may also lead to VMID conflicts.
-
-Its suggested that you create a new storage where only the node which you want
-to separate has access. This can be an new export on your NFS or a new Ceph
-pool, to name a few examples. Its just important that the exact same storage
-does not gets accessed by multiple clusters. After setting this storage up move
-all data from the node and its VMs to it. Then you are ready to separate the
+storage with another cluster, as storage locking doesn't work over the cluster
+boundary. Furthermore, it may also lead to VMID conflicts.
+
+It's suggested that you create a new storage, where only the node which you want
+to separate has access. This can be a new export on your NFS or a new Ceph
+pool, to name a few examples. It's just important that the exact same storage
+does not get accessed by multiple clusters. After setting up this storage, move
+all data and VMs from the node to it. Then you are ready to separate the
node from the cluster.
-WARNING: Ensure all shared resources are cleanly separated! You will run into
-conflicts and problems else.
+WARNING: Ensure that all shared resources are cleanly separated! Otherwise you
+will run into conflicts and problems.
-First stop the corosync and the pve-cluster services on the node:
+First, stop the corosync and pve-cluster services on the node:
[source,bash]
----
systemctl stop pve-cluster
systemctl stop corosync
----
-Start the cluster filesystem again in local mode:
+Start the cluster file system again in local mode:
[source,bash]
----
pmxcfs -l
[source,bash]
----
rm /etc/pve/corosync.conf
-rm /etc/corosync/*
+rm -r /etc/corosync/*
----
-You can now start the filesystem again as normal service:
+You can now start the file system again as a normal service:
[source,bash]
----
killall pmxcfs
systemctl start pve-cluster
----
-The node is now separated from the cluster. You can deleted it from a remaining
-node of the cluster with:
+The node is now separated from the cluster. You can deleted it from any
+remaining node of the cluster with:
[source,bash]
----
pvecm delnode oldnode
----
-If the command failed, because the remaining node in the cluster lost quorum
-when the now separate node exited, you may set the expected votes to 1 as a workaround:
+If the command fails due to a loss of quorum in the remaining node, you can set
+the expected votes to 1 as a workaround:
[source,bash]
----
pvecm expected 1
----
-And the repeat the 'pvecm delnode' command.
+And then repeat the 'pvecm delnode' command.
-Now switch back to the separated node, here delete all remaining files left
-from the old cluster. This ensures that the node can be added to another
-cluster again without problems.
+Now switch back to the separated node and delete all the remaining cluster
+files on it. This ensures that the node can be added to another cluster again
+without problems.
[source,bash]
----
----
As the configuration files from the other nodes are still in the cluster
-filesystem you may want to clean those up too. Remove simply the whole
-directory recursive from '/etc/pve/nodes/NODENAME', but check three times that
-you used the correct one before deleting it.
+file system, you may want to clean those up too. After making absolutely sure
+that you have the correct node name, you can simply remove the entire
+directory recursively from '/etc/pve/nodes/NODENAME'.
-CAUTION: The nodes SSH keys are still in the 'authorized_key' file, this means
-the nodes can still connect to each other with public key authentication. This
-should be fixed by removing the respective keys from the
+CAUTION: The node's SSH keys will remain in the 'authorized_key' file. This
+means that the nodes can still connect to each other with public key
+authentication. You should fix this by removing the respective keys from the
'/etc/pve/priv/authorized_keys' file.
+
Quorum
------
NOTE: {pve} assigns a single vote to each node by default.
+
Cluster Network
---------------
The cluster network is the core of a cluster. All messages sent over it have to
-be delivered reliable to all nodes in their respective order. In {pve} this
-part is done by corosync, an implementation of a high performance low overhead
-high availability development toolkit. It serves our decentralized
-configuration file system (`pmxcfs`).
+be delivered reliably to all nodes in their respective order. In {pve} this
+part is done by corosync, an implementation of a high performance, low overhead,
+high availability development toolkit. It serves our decentralized configuration
+file system (`pmxcfs`).
-[[cluster-network-requirements]]
+[[pvecm_cluster_network_requirements]]
Network Requirements
~~~~~~~~~~~~~~~~~~~~
-This needs a reliable network with latencies under 2 milliseconds (LAN
-performance) to work properly. While corosync can also use unicast for
-communication between nodes its **highly recommended** to have a multicast
-capable network. The network should not be used heavily by other members,
-ideally corosync runs on its own network.
-*never* share it with network where storage communicates too.
-Before setting up a cluster it is good practice to check if the network is fit
-for that purpose.
+The {pve} cluster stack requires a reliable network with latencies under 5
+milliseconds (LAN performance) between all nodes to operate stably. While on
+setups with a small node count a network with higher latencies _may_ work, this
+is not guaranteed and gets rather unlikely with more than three nodes and
+latencies above around 10 ms.
-* Ensure that all nodes are in the same subnet. This must only be true for the
- network interfaces used for cluster communication (corosync).
+The network should not be used heavily by other members, as while corosync does
+not uses much bandwidth it is sensitive to latency jitters; ideally corosync
+runs on its own physically separated network. Especially do not use a shared
+network for corosync and storage (except as a potential low-priority fallback
+in a xref:pvecm_redundancy[redundant] configuration).
-* Ensure all nodes can reach each other over those interfaces, using `ping` is
- enough for a basic test.
+Before setting up a cluster, it is good practice to check if the network is fit
+for that purpose. To ensure that the nodes can connect to each other on the
+cluster network, you can test the connectivity between them with the `ping`
+tool.
-* Ensure that multicast works in general and a high package rates. This can be
- done with the `omping` tool. The final "%loss" number should be < 1%.
-+
-[source,bash]
-----
-omping -c 10000 -i 0.001 -F -q NODE1-IP NODE2-IP ...
-----
-
-* Ensure that multicast communication works over an extended period of time.
- This covers up problems where IGMP snooping is activated on the network but
- no multicast querier is active. This test has a duration of around 10
- minutes.
-+
-[source,bash]
-----
-omping -c 600 -i 1 -q NODE1-IP NODE2-IP ...
-----
+If the {pve} firewall is enabled, ACCEPT rules for corosync will automatically
+be generated - no manual action is required.
-Your network is not ready for clustering if any of these test fails. Recheck
-your network configuration. Especially switches are notorious for having
-multicast disabled by default or IGMP snooping enabled with no IGMP querier
-active.
+NOTE: Corosync used Multicast before version 3.0 (introduced in {pve} 6.0).
+Modern versions rely on https://kronosnet.org/[Kronosnet] for cluster
+communication, which, for now, only supports regular UDP unicast.
-In smaller cluster its also an option to use unicast if you really cannot get
-multicast to work.
+CAUTION: You can still enable Multicast or legacy unicast by setting your
+transport to `udp` or `udpu` in your xref:pvecm_edit_corosync_conf[corosync.conf],
+but keep in mind that this will disable all cryptography and redundancy support.
+This is therefore not recommended.
Separate Cluster Network
~~~~~~~~~~~~~~~~~~~~~~~~
-When creating a cluster without any parameters the cluster network is generally
-shared with the Web UI and the VMs and its traffic. Depending on your setup
-even storage traffic may get sent over the same network. Its recommended to
-change that, as corosync is a time critical real time application.
+When creating a cluster without any parameters, the corosync cluster network is
+generally shared with the web interface and the VMs' network. Depending on
+your setup, even storage traffic may get sent over the same network. It's
+recommended to change that, as corosync is a time-critical, real-time
+application.
-Setting Up A New Network
+Setting Up a New Network
^^^^^^^^^^^^^^^^^^^^^^^^
-First you have to setup a new network interface. It should be on a physical
+First, you have to set up a new network interface. It should be on a physically
separate network. Ensure that your network fulfills the
-<<cluster-network-requirements,cluster network requirements>>.
+xref:pvecm_cluster_network_requirements[cluster network requirements].
Separate On Cluster Creation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-This is possible through the 'ring0_addr' and 'bindnet0_addr' parameter of
-the 'pvecm create' command used for creating a new cluster.
+This is possible via the 'linkX' parameters of the 'pvecm create'
+command, used for creating a new cluster.
-If you have setup a additional NIC with a static address on 10.10.10.1/25
-and want to send and receive all cluster communication over this interface
+If you have set up an additional NIC with a static address on 10.10.10.1/25,
+and want to send and receive all cluster communication over this interface,
you would execute:
[source,bash]
----
-pvecm create test --ring0_addr 10.10.10.1 --bindnet0_addr 10.10.10.0
+pvecm create test --link0 10.10.10.1
----
-To check if everything is working properly execute:
+To check if everything is working properly, execute:
[source,bash]
----
systemctl status corosync
----
-[[separate-cluster-net-after-creation]]
+Afterwards, proceed as described above to
+xref:pvecm_adding_nodes_with_separated_cluster_network[add nodes with a separated cluster network].
+
+[[pvecm_separate_cluster_net_after_creation]]
Separate After Cluster Creation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-You can do this also if you have already created a cluster and want to switch
+You can do this if you have already created a cluster and want to switch
its communication to another network, without rebuilding the whole cluster.
-This change may lead to short durations of quorum loss in the cluster, as nodes
+This change may lead to short periods of quorum loss in the cluster, as nodes
have to restart corosync and come up one after the other on the new network.
-Check how to <<edit-corosync-conf,edit the corosync.conf file>> first.
-The open it and you should see a file similar to:
+Check how to xref:pvecm_edit_corosync_conf[edit the corosync.conf file] first.
+Then, open it and you should see a file similar to:
----
logging {
}
totem {
- cluster_name: thomas-testcluster
+ cluster_name: testcluster
config_version: 3
- ip_version: ipv4
+ ip_version: ipv4-6
secauth: on
version: 2
interface {
- bindnetaddr: 192.168.30.50
- ringnumber: 0
+ linknumber: 0
}
}
----
-The first you want to do is add the 'name' properties in the node entries if
-you do not see them already. Those *must* match the node name.
+NOTE: `ringX_addr` actually specifies a corosync *link address*. The name "ring"
+is a remnant of older corosync versions that is kept for backwards
+compatibility.
+
+The first thing you want to do is add the 'name' properties in the node entries,
+if you do not see them already. Those *must* match the node name.
-Then replace the address from the 'ring0_addr' properties with the new
-addresses. You may use plain IP addresses or also hostnames here. If you use
-hostnames ensure that they are resolvable from all nodes.
+Then replace all addresses from the 'ring0_addr' properties of all nodes with
+the new addresses. You may use plain IP addresses or hostnames here. If you use
+hostnames, ensure that they are resolvable from all nodes (see also
+xref:pvecm_corosync_addresses[Link Address Types]).
-In my example I want to switch my cluster communication to the 10.10.10.1/25
-network. So I replace all 'ring0_addr' respectively. I also set the bindetaddr
-in the totem section of the config to an address of the new network. It can be
-any address from the subnet configured on the new network interface.
+In this example, we want to switch cluster communication to the
+10.10.10.0/25 network, so we change the 'ring0_addr' of each node respectively.
-After you increased the 'config_version' property the new configuration file
+NOTE: The exact same procedure can be used to change other 'ringX_addr' values
+as well. However, we recommend only changing one link address at a time, so
+that it's easier to recover if something goes wrong.
+
+After we increase the 'config_version' property, the new configuration file
should look like:
----
-
logging {
debug: off
to_syslog: yes
}
totem {
- cluster_name: thomas-testcluster
+ cluster_name: testcluster
config_version: 4
- ip_version: ipv4
+ ip_version: ipv4-6
secauth: on
version: 2
interface {
- bindnetaddr: 10.10.10.1
- ringnumber: 0
+ linknumber: 0
}
}
----
-Now after a final check whether all changed information is correct we save it
-and see again the <<edit-corosync-conf,edit corosync.conf file>> section to
-learn how to bring it in effect.
+Then, after a final check to see that all changed information is correct, we
+save it and once again follow the
+xref:pvecm_edit_corosync_conf[edit corosync.conf file] section to bring it into
+effect.
-As our change cannot be enforced live from corosync we have to do an restart.
+The changes will be applied live, so restarting corosync is not strictly
+necessary. If you changed other settings as well, or notice corosync
+complaining, you can optionally trigger a restart.
On a single node execute:
+
[source,bash]
----
systemctl restart corosync
----
-Now check if everything is fine:
+Now check if everything is okay:
[source,bash]
----
systemctl status corosync
----
-If corosync runs again correct restart corosync also on all other nodes.
+If corosync begins to work again, restart it on all other nodes too.
They will then join the cluster membership one by one on the new network.
-Redundant Ring Protocol
-~~~~~~~~~~~~~~~~~~~~~~~
-To avoid a single point of failure you should implement counter measurements.
-This can be on the hardware and operating system level through network bonding.
+[[pvecm_corosync_addresses]]
+Corosync Addresses
+~~~~~~~~~~~~~~~~~~
-Corosync itself offers also a possibility to add redundancy through the so
-called 'Redundant Ring Protocol'. This protocol allows running a second totem
-ring on another network, this network should be physically separated from the
-other rings network to actually increase availability.
+A corosync link address (for backwards compatibility denoted by 'ringX_addr' in
+`corosync.conf`) can be specified in two ways:
-RRP On Cluster Creation
-~~~~~~~~~~~~~~~~~~~~~~~
+* **IPv4/v6 addresses** can be used directly. They are recommended, since they
+are static and usually not changed carelessly.
-The 'pvecm create' command provides the additional parameters 'bindnetX_addr',
-'ringX_addr' and 'rrp_mode', can be used for RRP configuration.
+* **Hostnames** will be resolved using `getaddrinfo`, which means that by
+default, IPv6 addresses will be used first, if available (see also
+`man gai.conf`). Keep this in mind, especially when upgrading an existing
+cluster to IPv6.
-NOTE: See the <<corosync-conf-glossary,glossary>> if you do not know what each parameter means.
+CAUTION: Hostnames should be used with care, since the addresses they
+resolve to can be changed without touching corosync or the node it runs on -
+which may lead to a situation where an address is changed without thinking
+about implications for corosync.
-So if you have two networks, one on the 10.10.10.1/24 and the other on the
-10.10.20.1/24 subnet you would execute:
+A separate, static hostname specifically for corosync is recommended, if
+hostnames are preferred. Also, make sure that every node in the cluster can
+resolve all hostnames correctly.
+
+Since {pve} 5.1, while supported, hostnames will be resolved at the time of
+entry. Only the resolved IP is saved to the configuration.
+
+Nodes that joined the cluster on earlier versions likely still use their
+unresolved hostname in `corosync.conf`. It might be a good idea to replace
+them with IPs or a separate hostname, as mentioned above.
+
+
+[[pvecm_redundancy]]
+Corosync Redundancy
+-------------------
+
+Corosync supports redundant networking via its integrated Kronosnet layer by
+default (it is not supported on the legacy udp/udpu transports). It can be
+enabled by specifying more than one link address, either via the '--linkX'
+parameters of `pvecm`, in the GUI as **Link 1** (while creating a cluster or
+adding a new node) or by specifying more than one 'ringX_addr' in
+`corosync.conf`.
+
+NOTE: To provide useful failover, every link should be on its own
+physical network connection.
+
+Links are used according to a priority setting. You can configure this priority
+by setting 'knet_link_priority' in the corresponding interface section in
+`corosync.conf`, or, preferably, using the 'priority' parameter when creating
+your cluster with `pvecm`:
-[source,bash]
----
-pvecm create CLUSTERNAME -bindnet0_addr 10.10.10.1 -ring0_addr 10.10.10.1 \
--bindnet1_addr 10.10.20.1 -ring1_addr 10.10.20.1
+ # pvecm create CLUSTERNAME --link0 10.10.10.1,priority=15 --link1 10.20.20.1,priority=20
----
-RRP On A Created Cluster
-~~~~~~~~~~~~~~~~~~~~~~~~
+This would cause 'link1' to be used first, since it has the higher priority.
-When enabling an already running cluster to use RRP you will take similar steps
-as describe in
-<<separate-cluster-net-after-creation,separating the cluster network>>. You
-just do it on another ring.
+If no priorities are configured manually (or two links have the same priority),
+links will be used in order of their number, with the lower number having higher
+priority.
-First add a new `interface` subsection in the `totem` section, set its
-`ringnumber` property to `1`. Set the interfaces `bindnetaddr` property to an
-address of the subnet you have configured for your new ring.
-Further set the `rrp_mode` to `passive`, this is the only stable mode.
+Even if all links are working, only the one with the highest priority will see
+corosync traffic. Link priorities cannot be mixed, meaning that links with
+different priorities will not be able to communicate with each other.
-Then add to each node entry in the `nodelist` section its new `ring1_addr`
-property with the nodes additional ring address.
+Since lower priority links will not see traffic unless all higher priorities
+have failed, it becomes a useful strategy to specify networks used for
+other tasks (VMs, storage, etc.) as low-priority links. If worst comes to
+worst, a higher latency or more congested connection might be better than no
+connection at all.
-So if you have two networks, one on the 10.10.10.1/24 and the other on the
-10.10.20.1/24 subnet, the final configuration file should look like:
+Adding Redundant Links To An Existing Cluster
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To add a new link to a running configuration, first check how to
+xref:pvecm_edit_corosync_conf[edit the corosync.conf file].
+
+Then, add a new 'ringX_addr' to every node in the `nodelist` section. Make
+sure that your 'X' is the same for every node you add it to, and that it is
+unique for each node.
+
+Lastly, add a new 'interface', as shown below, to your `totem`
+section, replacing 'X' with the link number chosen above.
+
+Assuming you added a link with number 1, the new configuration file could look
+like this:
----
-totem {
- cluster_name: tweak
- config_version: 9
- ip_version: ipv4
- rrp_mode: passive
- secauth: on
- version: 2
- interface {
- bindnetaddr: 10.10.10.1
- ringnumber: 0
- }
- interface {
- bindnetaddr: 10.10.20.1
- ringnumber: 1
- }
+logging {
+ debug: off
+ to_syslog: yes
}
nodelist {
+
node {
- name: pvecm1
- nodeid: 1
+ name: due
+ nodeid: 2
quorum_votes: 1
- ring0_addr: 10.10.10.1
- ring1_addr: 10.10.20.1
+ ring0_addr: 10.10.10.2
+ ring1_addr: 10.20.20.2
}
- node {
- name: pvecm2
- nodeid: 2
+ node {
+ name: tre
+ nodeid: 3
quorum_votes: 1
- ring0_addr: 10.10.10.2
- ring1_addr: 10.10.20.2
+ ring0_addr: 10.10.10.3
+ ring1_addr: 10.20.20.3
+ }
+
+ node {
+ name: uno
+ nodeid: 1
+ quorum_votes: 1
+ ring0_addr: 10.10.10.1
+ ring1_addr: 10.20.20.1
}
- [...] # other cluster nodes here
}
-[...] # other remaining config sections here
+quorum {
+ provider: corosync_votequorum
+}
+
+totem {
+ cluster_name: testcluster
+ config_version: 4
+ ip_version: ipv4-6
+ secauth: on
+ version: 2
+ interface {
+ linknumber: 0
+ }
+ interface {
+ linknumber: 1
+ }
+}
+----
+
+The new link will be enabled as soon as you follow the last steps to
+xref:pvecm_edit_corosync_conf[edit the corosync.conf file]. A restart should not
+be necessary. You can check that corosync loaded the new link using:
+
+----
+journalctl -b -u corosync
+----
+
+It might be a good idea to test the new link by temporarily disconnecting the
+old link on one node and making sure that its status remains online while
+disconnected:
+
+----
+pvecm status
+----
+
+If you see a healthy cluster state, it means that your new link is being used.
+
+
+Role of SSH in {pve} Clusters
+-----------------------------
+
+{pve} utilizes SSH tunnels for various features.
+
+* Proxying console/shell sessions (node and guests)
++
+When using the shell for node B while being connected to node A, connects to a
+terminal proxy on node A, which is in turn connected to the login shell on node
+B via a non-interactive SSH tunnel.
+
+* VM and CT memory and local-storage migration in 'secure' mode.
++
+During the migration, one or more SSH tunnel(s) are established between the
+source and target nodes, in order to exchange migration information and
+transfer memory and disk contents.
+
+* Storage replication
+
+SSH setup
+~~~~~~~~~
+
+On {pve} systems, the following changes are made to the SSH configuration/setup:
+
+* the `root` user's SSH client config gets setup to prefer `AES` over `ChaCha20`
+
+* the `root` user's `authorized_keys` file gets linked to
+ `/etc/pve/priv/authorized_keys`, merging all authorized keys within a cluster
+
+* `sshd` is configured to allow logging in as root with a password
+
+NOTE: Older systems might also have `/etc/ssh/ssh_known_hosts` set up as symlink
+pointing to `/etc/pve/priv/known_hosts`, containing a merged version of all
+node host keys. This system was replaced with explicit host key pinning in
+`pve-cluster <<INSERT VERSION>>`, the symlink can be deconfigured if still in
+place by running `pvecm updatecerts --unmerge-known-hosts`.
+
+Pitfalls due to automatic execution of `.bashrc` and siblings
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In case you have a custom `.bashrc`, or similar files that get executed on
+login by the configured shell, `ssh` will automatically run it once the session
+is established successfully. This can cause some unexpected behavior, as those
+commands may be executed with root permissions on any of the operations
+described above. This can cause possible problematic side-effects!
+
+In order to avoid such complications, it's recommended to add a check in
+`/root/.bashrc` to make sure the session is interactive, and only then run
+`.bashrc` commands.
+
+You can add this snippet at the beginning of your `.bashrc` file:
+
+----
+# Early exit if not running interactively to avoid side-effects!
+case $- in
+ *i*) ;;
+ *) return;;
+esac
+----
+
+Corosync External Vote Support
+------------------------------
+
+This section describes a way to deploy an external voter in a {pve} cluster.
+When configured, the cluster can sustain more node failures without
+violating safety properties of the cluster communication.
+
+For this to work, there are two services involved:
+
+* A QDevice daemon which runs on each {pve} node
+
+* An external vote daemon which runs on an independent server
+
+As a result, you can achieve higher availability, even in smaller setups (for
+example 2+1 nodes).
+
+QDevice Technical Overview
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The Corosync Quorum Device (QDevice) is a daemon which runs on each cluster
+node. It provides a configured number of votes to the cluster's quorum
+subsystem, based on an externally running third-party arbitrator's decision.
+Its primary use is to allow a cluster to sustain more node failures than
+standard quorum rules allow. This can be done safely as the external device
+can see all nodes and thus choose only one set of nodes to give its vote.
+This will only be done if said set of nodes can have quorum (again) after
+receiving the third-party vote.
+
+Currently, only 'QDevice Net' is supported as a third-party arbitrator. This is
+a daemon which provides a vote to a cluster partition, if it can reach the
+partition members over the network. It will only give votes to one partition
+of a cluster at any time.
+It's designed to support multiple clusters and is almost configuration and
+state free. New clusters are handled dynamically and no configuration file
+is needed on the host running a QDevice.
+
+The only requirements for the external host are that it needs network access to
+the cluster and to have a corosync-qnetd package available. We provide a package
+for Debian based hosts, and other Linux distributions should also have a package
+available through their respective package manager.
+
+NOTE: Unlike corosync itself, a QDevice connects to the cluster over TCP/IP.
+The daemon can also run outside the LAN of the cluster and isn't limited to the
+low latencies requirements of corosync.
+
+Supported Setups
+~~~~~~~~~~~~~~~~
+
+We support QDevices for clusters with an even number of nodes and recommend
+it for 2 node clusters, if they should provide higher availability.
+For clusters with an odd node count, we currently discourage the use of
+QDevices. The reason for this is the difference in the votes which the QDevice
+provides for each cluster type. Even numbered clusters get a single additional
+vote, which only increases availability, because if the QDevice
+itself fails, you are in the same position as with no QDevice at all.
+
+On the other hand, with an odd numbered cluster size, the QDevice provides
+'(N-1)' votes -- where 'N' corresponds to the cluster node count. This
+alternative behavior makes sense; if it had only one additional vote, the
+cluster could get into a split-brain situation. This algorithm allows for all
+nodes but one (and naturally the QDevice itself) to fail. However, there are two
+drawbacks to this:
+
+* If the QNet daemon itself fails, no other node may fail or the cluster
+ immediately loses quorum. For example, in a cluster with 15 nodes, 7
+ could fail before the cluster becomes inquorate. But, if a QDevice is
+ configured here and it itself fails, **no single node** of the 15 may fail.
+ The QDevice acts almost as a single point of failure in this case.
+
+* The fact that all but one node plus QDevice may fail sounds promising at
+ first, but this may result in a mass recovery of HA services, which could
+ overload the single remaining node. Furthermore, a Ceph server will stop
+ providing services if only '((N-1)/2)' nodes or less remain online.
+
+If you understand the drawbacks and implications, you can decide yourself if
+you want to use this technology in an odd numbered cluster setup.
+
+QDevice-Net Setup
+~~~~~~~~~~~~~~~~~
+
+We recommend running any daemon which provides votes to corosync-qdevice as an
+unprivileged user. {pve} and Debian provide a package which is already
+configured to do so.
+The traffic between the daemon and the cluster must be encrypted to ensure a
+safe and secure integration of the QDevice in {pve}.
+
+First, install the 'corosync-qnetd' package on your external server
+
+----
+external# apt install corosync-qnetd
+----
+
+and the 'corosync-qdevice' package on all cluster nodes
+
+----
+pve# apt install corosync-qdevice
+----
+
+After doing this, ensure that all the nodes in the cluster are online.
+
+You can now set up your QDevice by running the following command on one
+of the {pve} nodes:
+
+----
+pve# pvecm qdevice setup <QDEVICE-IP>
+----
+
+The SSH key from the cluster will be automatically copied to the QDevice.
+
+NOTE: Make sure to setup key-based access for the root user on your external
+server, or temporarily allow root login with password during the setup phase.
+If you receive an error such as 'Host key verification failed.' at this
+stage, running `pvecm updatecerts` could fix the issue.
+
+After all the steps have successfully completed, you will see "Done". You can
+verify that the QDevice has been set up with:
+
+----
+pve# pvecm status
+
+...
+
+Votequorum information
+~~~~~~~~~~~~~~~~~~~~~
+Expected votes: 3
+Highest expected: 3
+Total votes: 3
+Quorum: 2
+Flags: Quorate Qdevice
+
+Membership information
+~~~~~~~~~~~~~~~~~~~~~~
+ Nodeid Votes Qdevice Name
+ 0x00000001 1 A,V,NMW 192.168.22.180 (local)
+ 0x00000002 1 A,V,NMW 192.168.22.181
+ 0x00000000 1 Qdevice
----
-Bring it in effect like described in the
-<<edit-corosync-conf,edit the corosync.conf file>> section.
+[[pvecm_qdevice_status_flags]]
+QDevice Status Flags
+^^^^^^^^^^^^^^^^^^^^
-This is a change which cannot take live in effect and needs at least a restart
-of corosync. Recommended is a restart of the whole cluster.
+The status output of the QDevice, as seen above, will usually contain three
+columns:
+
+* `A` / `NA`: Alive or Not Alive. Indicates if the communication to the external
+ `corosync-qnetd` daemon works.
+* `V` / `NV`: If the QDevice will cast a vote for the node. In a split-brain
+ situation, where the corosync connection between the nodes is down, but they
+ both can still communicate with the external `corosync-qnetd` daemon,
+ only one node will get the vote.
+* `MW` / `NMW`: Master wins (`MV`) or not (`NMW`). Default is `NMW`, see
+ footnote:[`votequorum_qdevice_master_wins` manual page
+ https://manpages.debian.org/bookworm/libvotequorum-dev/votequorum_qdevice_master_wins.3.en.html].
+* `NR`: QDevice is not registered.
+
+NOTE: If your QDevice is listed as `Not Alive` (`NA` in the output above),
+ensure that port `5403` (the default port of the qnetd server) of your external
+server is reachable via TCP/IP!
+
+
+Frequently Asked Questions
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Tie Breaking
+^^^^^^^^^^^^
+
+In case of a tie, where two same-sized cluster partitions cannot see each other
+but can see the QDevice, the QDevice chooses one of those partitions randomly
+and provides a vote to it.
+
+Possible Negative Implications
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+For clusters with an even node count, there are no negative implications when
+using a QDevice. If it fails to work, it is the same as not having a QDevice
+at all.
+
+Adding/Deleting Nodes After QDevice Setup
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If you want to add a new node or remove an existing one from a cluster with a
+QDevice setup, you need to remove the QDevice first. After that, you can add or
+remove nodes normally. Once you have a cluster with an even node count again,
+you can set up the QDevice again as described previously.
+
+Removing the QDevice
+^^^^^^^^^^^^^^^^^^^^
+
+If you used the official `pvecm` tool to add the QDevice, you can remove it
+by running:
+
+----
+pve# pvecm qdevice remove
+----
+
+//Still TODO
+//^^^^^^^^^^
+//There is still stuff to add here
-If you cannot reboot the whole cluster ensure no High Availability services are
-configured and the stop the corosync service on all nodes. After corosync is
-stopped on all nodes start it one after the other again.
Corosync Configuration
----------------------
-The `/ect/pve/corosync.conf` file plays a central role in {pve} cluster. It
-controls the cluster member ship and its network.
-For reading more about it check the corosync.conf man page:
+The `/etc/pve/corosync.conf` file plays a central role in a {pve} cluster. It
+controls the cluster membership and its network.
+For further information about it, check the corosync.conf man page:
[source,bash]
----
man corosync.conf
----
-For node membership you should always use the `pvecm` tool provided by {pve}.
+For node membership, you should always use the `pvecm` tool provided by {pve}.
You may have to edit the configuration file manually for other changes.
Here are a few best practice tips for doing this.
-[[edit-corosync-conf]]
+[[pvecm_edit_corosync_conf]]
Edit corosync.conf
~~~~~~~~~~~~~~~~~~
-Editing the corosync.conf file can be not always straight forward. There are
-two on each cluster, one in `/etc/pve/corosync.conf` and the other in
+Editing the corosync.conf file is not always very straightforward. There are
+two on each cluster node, one in `/etc/pve/corosync.conf` and the other in
`/etc/corosync/corosync.conf`. Editing the one in our cluster file system will
propagate the changes to the local one, but not vice versa.
-The configuration will get updated automatically as soon as the file changes.
-This means changes which can be integrated in a running corosync will take
-instantly effect. So you should always make a copy and edit that instead, to
-avoid triggering some unwanted changes by an in between safe.
+The configuration will get updated automatically, as soon as the file changes.
+This means that changes which can be integrated in a running corosync will take
+effect immediately. Thus, you should always make a copy and edit that instead,
+to avoid triggering unintended changes when saving the file while editing.
[source,bash]
----
cp /etc/pve/corosync.conf /etc/pve/corosync.conf.new
----
-Then open the Config file with your favorite editor, `nano` and `vim.tiny` are
-preinstalled on {pve} for example.
+Then, open the config file with your favorite editor, such as `nano` or
+`vim.tiny`, which come pre-installed on every {pve} node.
-NOTE: Always increment the 'config_version' number on configuration changes,
+NOTE: Always increment the 'config_version' number after configuration changes;
omitting this can lead to problems.
-After making the necessary changes create another copy of the current working
+After making the necessary changes, create another copy of the current working
configuration file. This serves as a backup if the new configuration fails to
-apply or makes problems in other ways.
+apply or causes other issues.
[source,bash]
----
cp /etc/pve/corosync.conf /etc/pve/corosync.conf.bak
----
-Then move the new configuration file over the old one:
+Then replace the old configuration file with the new one:
[source,bash]
----
mv /etc/pve/corosync.conf.new /etc/pve/corosync.conf
----
-You may check with the commands
+You can check if the changes could be applied automatically, using the following
+commands:
[source,bash]
----
systemctl status corosync
journalctl -b -u corosync
----
-If the change could applied automatically. If not you may have to restart the
+If the changes could not be applied automatically, you may have to restart the
corosync service via:
[source,bash]
----
systemctl restart corosync
----
-On errors check the troubleshooting section below.
+On errors, check the troubleshooting section below.
Troubleshooting
~~~~~~~~~~~~~~~
[...]
----
-It means that the hostname you set for corosync 'ringX_addr' in the
+It means that the hostname you set for a corosync 'ringX_addr' in the
configuration could not be resolved.
-
Write Configuration When Not Quorate
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-If you need to change '/etc/pve/corosync.conf' on an node with no quorum, and you
-know what you do, use:
+If you need to change '/etc/pve/corosync.conf' on a node with no quorum, and you
+understand what you are doing, use:
[source,bash]
----
pvecm expected 1
----
This sets the expected vote count to 1 and makes the cluster quorate. You can
-now fix your configuration, or revert it back to the last working backup.
+then fix your configuration, or revert it back to the last working backup.
-This is not enough if corosync cannot start anymore. Here its best to edit the
-local copy of the corosync configuration in '/etc/corosync/corosync.conf' so
-that corosync can start again. Ensure that on all nodes this configuration has
-the same content to avoid split brains. If you are not sure what went wrong
-it's best to ask the Proxmox Community to help you.
+This is not enough if corosync cannot start anymore. In that case, it is best to
+edit the local copy of the corosync configuration in
+'/etc/corosync/corosync.conf', so that corosync can start again. Ensure that on
+all nodes, this configuration has the same content to avoid split-brain
+situations.
-[[corosync-conf-glossary]]
+[[pvecm_corosync_conf_glossary]]
Corosync Configuration Glossary
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ringX_addr::
-This names the different ring addresses for the corosync totem rings used for
-the cluster communication.
-
-bindnetaddr::
-Defines to which interface the ring should bind to. It may be any address of
-the subnet configured on the interface we want to use. In general its the
-recommended to just use an address a node uses on this interface.
-
-rrp_mode::
-Specifies the mode of the redundant ring protocol and may be passive, active or
-none. Note that use of active is highly experimental and not official
-supported. Passive is the preferred mode, it may double the cluster
-communication throughput and increases availability.
+This names the different link addresses for the Kronosnet connections between
+nodes.
Cluster Cold Start
(``UPS'', also called ``battery backup'') to avoid this state, especially if
you want HA.
-On node startup, service `pve-manager` is started and waits for
+On node startup, the `pve-guests` service is started and waits for
quorum. Once quorate, it starts all guests which have the `onboot`
flag set.
When you turn on nodes, or when power comes back after power failure,
-it is likely that some nodes boots faster than others. Please keep in
+it is likely that some nodes will boot faster than others. Please keep in
mind that guest startup is delayed until you reach quorum.
+[[pvecm_next_id_range]]
+Guest VMID Auto-Selection
+------------------------
+
+When creating new guests the web interface will ask the backend for a free VMID
+automatically. The default range for searching is `100` to `1000000` (lower
+than the maximal allowed VMID enforced by the schema).
+
+Sometimes admins either want to allocate new VMIDs in a separate range, for
+example to easily separate temporary VMs with ones that choose a VMID manually.
+Other times its just desired to provided a stable length VMID, for which
+setting the lower boundary to, for example, `100000` gives much more room for.
+
+To accommodate this use case one can set either lower, upper or both boundaries
+via the `datacenter.cfg` configuration file, which can be edited in the web
+interface under 'Datacenter' -> 'Options'.
+
+NOTE: The range is only used for the next-id API call, so it isn't a hard
+limit.
+
Guest Migration
---------------
Migrating virtual guests to other nodes is a useful feature in a
cluster. There are settings to control the behavior of such
migrations. This can be done via the configuration file
-`datacenter.cfg` or for a specific migration via API or command line
+`datacenter.cfg` or for a specific migration via API or command-line
parameters.
+It makes a difference if a guest is online or offline, or if it has
+local resources (like a local disk).
+
+For details about virtual machine migration, see the
+xref:qm_migration[QEMU/KVM Migration Chapter].
+
+For details about container migration, see the
+xref:pct_migration[Container Migration Chapter].
Migration Type
~~~~~~~~~~~~~~
-The migration type defines if the migration data should be sent over a
+The migration type defines if the migration data should be sent over an
encrypted (`secure`) channel or an unencrypted (`insecure`) one.
-Setting the migration type to insecure means that the RAM content of a
-virtual guest gets also transfered unencrypted, which can lead to
+Setting the migration type to `insecure` means that the RAM content of a
+virtual guest is also transferred unencrypted, which can lead to
information disclosure of critical data from inside the guest (for
-example passwords or encryption keys).
+example, passwords or encryption keys).
Therefore, we strongly recommend using the secure channel if you do
not have full control over the network and can not guarantee that no
-one is eavesdropping to it.
+one is eavesdropping on it.
NOTE: Storage migration does not follow this setting. Currently, it
always sends the storage content over a secure channel.
Encryption requires a lot of computing power, so this setting is often
-changed to "unsafe" to achieve better performance. The impact on
+changed to `insecure` to achieve better performance. The impact on
modern systems is lower because they implement AES encryption in
hardware. The performance impact is particularly evident in fast
-networks where you can transfer 10 Gbps or more.
-
+networks, where you can transfer 10 Gbps or more.
Migration Network
~~~~~~~~~~~~~~~~~
By default, {pve} uses the network in which cluster communication
-takes place to send the migration traffic. This is not optimal because
+takes place to send the migration traffic. This is not optimal both because
sensitive cluster traffic can be disrupted and this network may not
have the best bandwidth available on the node.
Setting the migration network parameter allows the use of a dedicated
-network for the entire migration traffic. In addition to the memory,
+network for all migration traffic. In addition to the memory,
this also affects the storage traffic for offline migrations.
-The migration network is set as a network in the CIDR notation. This
-has the advantage that you do not have to set individual IP addresses
-for each node. {pve} can determine the real address on the
-destination node from the network specified in the CIDR form. To
-enable this, the network must be specified so that each node has one,
-but only one IP in the respective network.
-
+The migration network is set as a network using CIDR notation. This
+has the advantage that you don't have to set individual IP addresses
+for each node. {pve} can determine the real address on the
+destination node from the network specified in the CIDR form. To
+enable this, the network must be specified so that each node has exactly one
+IP in the respective network.
Example
^^^^^^^
-We assume that we have a three-node setup with three separate
+We assume that we have a three-node setup, with three separate
networks. One for public communication with the Internet, one for
-cluster communication and a very fast one, which we want to use as a
+cluster communication, and a very fast one, which we want to use as a
dedicated network for migration.
A network configuration for such a setup might look as follows:
----
-iface eth0 inet manual
+iface eno1 inet manual
# public network
auto vmbr0
iface vmbr0 inet static
- address 192.X.Y.57
- netmask 255.255.250.0
+ address 192.X.Y.57/24
gateway 192.X.Y.1
- bridge_ports eth0
- bridge_stp off
- bridge_fd 0
+ bridge-ports eno1
+ bridge-stp off
+ bridge-fd 0
# cluster network
-auto eth1
-iface eth1 inet static
- address 10.1.1.1
- netmask 255.255.255.0
+auto eno2
+iface eno2 inet static
+ address 10.1.1.1/24
# fast network
-auto eth2
-iface eth2 inet static
- address 10.1.2.1
- netmask 255.255.255.0
+auto eno3
+iface eno3 inet static
+ address 10.1.2.1/24
----
Here, we will use the network 10.1.2.0/24 as a migration network. For
a single migration, you can do this using the `migration_network`
-parameter of the command line tool:
+parameter of the command-line tool:
----
# qm migrate 106 tre --online --migration_network 10.1.2.0/24
----
NOTE: The migration type must always be set when the migration network
-gets set in `/etc/pve/datacenter.cfg`.
+is set in `/etc/pve/datacenter.cfg`.
ifdef::manvolnum[]
projects / pve-docs.git / blobdiff