+[[chapter_pvecm]]
ifdef::manvolnum[]
pvecm(1)
========
* 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.
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 often common use to reference all other nodenames in `/etc/hosts`
+with their IP this is not strictly necessary for a cluster, which normally uses
+multicast, to work. It maybe useful as you then can connect from one node to
+the other with SSH through the easier to remember node name.
+[[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.
+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. 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.
+
+
+[[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.
To check the state of cluster:
+----
# pvecm status
+----
.Cluster status after adding 4 nodes
----
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]]
Adding Nodes With Separated Cluster Network
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.
-Log in to one remaining node via ssh. Issue a `pvecm nodes` command to
-identify the node ID:
-
-----
-hp1# pvecm status
-
-Quorum information
-~~~~~~~~~~~~~~~~~~
-Date: Mon Apr 20 12:30:13 2015
-Quorum provider: corosync_votequorum
-Nodes: 4
-Node ID: 0x00000001
-Ring ID: 1928
-Quorate: Yes
-
-Votequorum information
-~~~~~~~~~~~~~~~~~~~~~~
-Expected votes: 4
-Highest expected: 4
-Total votes: 4
-Quorum: 2
-Flags: Quorate
-
-Membership information
-~~~~~~~~~~~~~~~~~~~~~~
- Nodeid Votes Name
-0x00000001 1 192.168.15.91 (local)
-0x00000002 1 192.168.15.92
-0x00000003 1 192.168.15.93
-0x00000004 1 192.168.15.94
-----
-
-IMPORTANT: at this point you must power off the node to be removed and
-make sure that it will not power on again (in the network) as it
-is.
+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
4 1 hp4
----
-Log in to one remaining node via ssh. Issue the delete command (here
-deleting node `hp4`):
+At this point you must power off hp4 and
+make sure that it will not power on again (in the network) as it
+is.
+
+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.
+
+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
Expected votes: 3
Highest expected: 3
Total votes: 3
-Quorum: 3
+Quorum: 2
Flags: Quorate
Membership information
0x00000003 1 192.168.15.92
----
-IMPORTANT: as said above, it is very important 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.
-
If, for whatever reason, you want that this server joins the same
cluster again, you have to
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
the node from the cluster. A {pve} cluster cannot share the exact same
-storage with another cluster, as it leads to VMID conflicts.
+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
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
* 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
+ 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 ...
This is possible through the 'ring0_addr' and 'bindnet0_addr' parameter 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
+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
you would 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>>.
+
[[separate-cluster-net-after-creation]]
Separate After Cluster Creation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
hostnames ensure that they are resolvable from all nodes.
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
+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.
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.
-bindnet1_addr 10.10.20.1 -ring1_addr 10.10.20.1
----
-RRP On A Created Cluster
+RRP On Existing Clusters
~~~~~~~~~~~~~~~~~~~~~~~~
-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.
+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`.
First add a new `interface` subsection in the `totem` section, set its
`ringnumber` property to `1`. Set the interfaces `bindnetaddr` property to an
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 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 and thus does not need a multicast capable network between itself and
+the cluster. In fact the daemon may run outside of the 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 Stretch 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 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
+
+...
+
+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 ist still stuff to add here
+
+
Corosync Configuration
----------------------
-The `/ect/pve/corosync.conf` file plays a central role in {pve} cluster. It
+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:
[source,bash]
(``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.
`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
+virtual guest gets also transferred unencrypted, which can lead to
information disclosure of critical data from inside the guest (for
example passwords or encryption keys).
A network configuration for such a setup might look as follows:
----
-iface eth0 inet manual
+iface eno1 inet manual
# public network
auto vmbr0
address 192.X.Y.57
netmask 255.255.250.0
gateway 192.X.Y.1
- bridge_ports eth0
+ bridge_ports eno1
bridge_stp off
bridge_fd 0
# cluster network
-auto eth1
-iface eth1 inet static
+auto eno2
+iface eno2 inet static
address 10.1.1.1
netmask 255.255.255.0
# fast network
-auto eth2
-iface eth2 inet static
+auto eno3
+iface eno3 inet static
address 10.1.2.1
netmask 255.255.255.0
----
projects / pve-docs.git / blobdiff