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 5404 and 5405
+ for corosync to work.
* Date and time have to be synchronized.
* 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.
+* Root password of a cluster node is required for adding nodes.
+
+NOTE: It is not possible to mix {pve} 3.x and earlier with {pve} 4.X cluster
+nodes.
+
+NOTE: While it's possible for {pve} 4.4 and {pve} 5.0 this is not supported as
+production configuration and should only used temporarily during upgrading the
+whole cluster from one to another major version.
+
+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
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`.
+Currently the cluster creation can either be done on the console (login via
+`ssh`) or the API, which we have a GUI implementation for (__Datacenter ->
+Cluster__).
+
+While it's common to reference all nodenames 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 the other with SSH via the easier to remember node name (see also
+xref:pvecm_corosync_addresses[Link Address Types]). Note that we always
+recommend to reference nodes by their IP addresses in the cluster configuration.
+
[[pvecm_create_cluster]]
Create the Cluster
------------------
Login via `ssh` to the first {pve} node. Use a unique name for your cluster.
-This name cannot be changed later.
+This name cannot be changed later. The cluster name follows the same rules as
+node names.
- hp1# pvecm create YOUR-CLUSTER-NAME
+----
+ hp1# pvecm create CLUSTERNAME
+----
-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.
+NOTE: It is possible to create multiple clusters in the same physical or logical
+network. Use unique cluster names if you do so. To avoid human confusion, it is
+also recommended to choose different names even if clusters do not share the
+cluster network.
To check the state of your cluster use:
+----
hp1# pvecm status
+----
Multiple Clusters In Same Network
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is possible to create multiple clusters in the same physical or logical
-network. Each cluster must have a unique name, which is used to generate the
-cluster's multicast group address. As long as no duplicate cluster names are
-configured in one network segment, the different clusters won't interfere with
-each other.
-
-If multiple clusters operate in a single network it may be beneficial to setup
-an IGMP querier and enable IGMP Snooping in said network. This may reduce the
-load of the network significantly because multicast packets are only delivered
-to endpoints of the respective member nodes.
+network. Each such cluster must have a unique name, this does not only helps
+admins to distinguish on which cluster they currently operate, it is also
+required to avoid possible clashes in the cluster communication stack.
+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.
+----
hp2# pvecm add IP-ADDRESS-CLUSTER
+----
-For `IP-ADDRESS-CLUSTER` use the IP from an existing cluster node.
+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
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
----
Quorum provider: corosync_votequorum
Nodes: 4
Node ID: 0x00000001
-Ring ID: 1928
+Ring ID: 1/8
Quorate: Yes
Votequorum information
Expected votes: 4
Highest expected: 4
Total votes: 4
-Quorum: 2
+Quorum: 3
Flags: Quorate
Membership information
If you only want the list of all nodes use:
+----
# pvecm nodes
+----
.List nodes in a cluster
----
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:
+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.
Remove a Cluster Node
After powering off the node hp4, we can safely remove it from the cluster.
+----
hp1# pvecm delnode hp4
+----
If the operation succeeds no output is returned, just check the node
list again with `pvecm nodes` or `pvecm status`. You should see
Quorum provider: corosync_votequorum
Nodes: 3
Node ID: 0x00000001
-Ring ID: 1992
+Ring ID: 1/8
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
* then join it, as explained in the previous section.
+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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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
+to separate has access. This can be a 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
node from the cluster.
-WARNING: Ensure all shared resources are cleanly separated! You will run into
-conflicts and problems else.
+WARNING: Ensure 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:
[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
should be fixed 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
+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.
+performance) to work properly. The network should not be used heavily by other
+members, ideally corosync runs on its own network. Do not use a shared network
+for corosync and storage (except as a potential low-priority fallback in a
+xref:pvecm_redundancy[redundant] configuration).
-Before setting up a cluster it is good practice to check if the network is fit
-for that purpose.
+Before setting up a cluster, it is good practice to check if the network is fit
+for that purpose. To make sure the nodes can connect to each other on the
+cluster network, you can test the connectivity between them with the `ping`
+tool.
-* Ensure that all nodes are in the same subnet. This must only be true for the
- network interfaces used for cluster communication (corosync).
+If the {pve} firewall is enabled, ACCEPT rules for corosync will automatically
+be generated - no manual action is required.
-* Ensure all nodes can reach each other over those interfaces, using `ping` is
- enough for a basic test.
+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.
-* 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 uncovers 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 ...
-----
-
-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.
-
-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 UI and the VMs and their 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.
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 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
+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:
systemctl status corosync
----
-Afterwards, proceed as descripted in the section to
-<<adding-nodes-with-separated-cluster-network,add nodes with a separated cluster network>>.
+Afterwards, proceed as described above to
+xref:pvecm_adding_nodes_with_separated_cluster_network[add nodes with a separated cluster network].
-[[separate-cluster-net-after-creation]]
+[[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
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 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])
-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.
+In this example, we want to switch the cluster communication to the
+10.10.10.1/25 network. So we replace all 'ring0_addr' respectively.
-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 bindnetaddr
-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.
+NOTE: The exact same procedure can be used to change other 'ringX_addr' values
+as well, although we recommend to not change multiple addresses at once, to make
+it easier to recover if something goes wrong.
-After you increased the 'config_version' property the new configuration file
+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 if 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
If corosync runs again correct restart corosync also on all other nodes.
They will then join the cluster membership one by one on the new network.
-[[pvecm_rrp]]
-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** will 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 per
+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 address 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 seperate, 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 then 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 seperate 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` (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, preferrably, 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=20 --link1 10.20.20.1,priority=15
----
-RRP On Existing Clusters
-~~~~~~~~~~~~~~~~~~~~~~~~
+This would cause 'link1' to be used first, since it has the lower priority.
+
+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.
+
+Even if all links are working, only the one with the highest priority will see
+corosync traffic. Link priorities cannot be mixed, i.e. links with different
+priorities will not be able to communicate with each other.
+
+Since lower priority links will not see traffic unless all higher priorities
+have failed, it becomes a useful strategy to specify even 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.
+
+Adding Redundant Links To An Existing Cluster
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-You will take similar steps as described in
-<<separate-cluster-net-after-creation,separating the cluster network>> to
-enable RRP on an already running cluster. The single difference is, that you
-will add `ring1` and use it instead of `ring0`.
+To add a new link to a running configuration, first check how to
+xref:pvecm_edit_corosync_conf[edit the corosync.conf file].
-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.
+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.
-Then add to each node entry in the `nodelist` section its new `ring1_addr`
-property with the nodes additional ring address.
+Lastly, add a new 'interface', as shown below, to your `totem`
+section, replacing 'X' with your link number chosen above.
-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:
+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.
+
+
+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 so called 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 Quroum Device (QDevice) is a daemon which runs on each cluster
+node. It provides a configured number of votes to the clusters quorum
+subsystem based on an external 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) when
+receiving the third-party vote.
+
+Currently only 'QDevice Net' is supported as a third-party arbitrator. It is
+a daemon which provides a vote to a cluster partition if it can reach the
+partition members over the network. It will give only 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 external host has the only requirement that it needs network access to the
+cluster and a corosync-qnetd package available. We provide such a package
+for Debian based hosts, other Linux distributions should also have a package
+available through their respective package manager.
+
+NOTE: In contrast to corosync itself, a QDevice connects to the cluster over
+TCP/IP. The daemon may even run outside of the clusters LAN and can have longer
+latencies than 2 ms.
+
+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 discourage the use of QDevices
+currently. The reason for this, is the difference of the votes the QDevice
+provides for each cluster type. Even numbered clusters get single additional
+vote, with this we can only increase availability, i.e. if the QDevice
+itself fails we are in the same situation as with no QDevice at all.
+
+Now, with an odd numbered cluster size the QDevice provides '(N-1)' votes --
+where 'N' corresponds to the cluster node count. This difference makes
+sense, if we had only one additional vote the cluster can get into a split
+brain situation.
+This algorithm would allow that all nodes but one (and naturally the
+QDevice itself) could fail.
+There are two drawbacks with 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 said QDevice fails itself **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 sound promising at
+ first, but this may result in a mass recovery of HA services that would
+ overload the single node left. Also ceph server will stop to provide
+ services after only '((N-1)/2)' nodes are online.
+
+If you understand the drawbacks and implications you can decide yourself if
+you should use this technology in an odd numbered cluster setup.
+
+QDevice-Net Setup
+~~~~~~~~~~~~~~~~~
+
+We recommend to run any daemon which provides votes to corosync-qdevice as an
+unprivileged user. {pve} and Debian provides 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 QDevice integration in {pve}.
+
+First install the 'corosync-qnetd' package on your external server and
+the 'corosync-qdevice' package on all cluster nodes.
+
+After that, ensure that all your nodes on the cluster are online.
+
+You can now easily 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. You
+might need to enter an SSH password during this step.
+
+After you enter the password and all the steps are successfully completed, you
+will see "Done". You can check the status now:
----
+pve# pvecm status
-Bring it in effect like described in the
-<<edit-corosync-conf,edit the corosync.conf file>> section.
+...
-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.
+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
+
+----
+
+which means the QDevice is set up.
+
+Frequently Asked Questions
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Tie Breaking
+^^^^^^^^^^^^
+
+In case of a tie, where two same-sized cluster partitions cannot see each other
+but the QDevice, the QDevice chooses randomly one of those partitions and
+provides a vote to it.
+
+Possible Negative Implications
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+For clusters with an even node count there are no negative implications when
+setting up a QDevice. If it fails to work, you are as good as without 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 above.
+
+Removing the QDevice
+^^^^^^^^^^^^^^^^^^^^
+
+If you used the official `pvecm` tool to add the QDevice, you can remove it
+trivially 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 `/etc/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
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.
+effect immediately. So you should always make a copy and edit that instead, to
+avoid triggering some unwanted changes by an in-between safe.
[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, `nano` and `vim.tiny` are
+preinstalled on any {pve} node for example.
NOTE: Always increment the 'config_version' number on configuration changes,
omitting this can lead to problems.
journalctl -b -u corosync
----
-If the change could applied automatically. If not you may have to restart the
+If the change could be applied automatically. If not you may have to restart the
corosync service via:
[source,bash]
----
It means that the hostname you set for corosync 'ringX_addr' in the
configuration could not be resolved.
-
Write Configuration When Not Quorate
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
it's best to ask the Proxmox Community to help you.
-[[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
local resources (like a local disk).
For Details about Virtual Machine Migration see the
-xref:qm_migration[QEMU/KVM Migration Chapter]
+xref:qm_migration[QEMU/KVM Migration Chapter].
For Details about Container Migration see the
-xref:pct_migration[Container Migration Chapter]
+xref:pct_migration[Container Migration Chapter].
Migration Type
~~~~~~~~~~~~~~
hardware. The performance impact is particularly evident in fast
networks where you can transfer 10 Gbps or more.
-
Migration Network
~~~~~~~~~~~~~~~~~
enable this, the network must be specified so that each node has one,
but only one IP in the respective network.
-
Example
^^^^^^^
projects / pve-docs.git / blobdiff