9 pvecm - Proxmox VE Cluster Manager
14 include::pvecm.1-synopsis.adoc[]
26 The {PVE} cluster manager `pvecm` is a tool to create a group of
27 physical servers. Such a group is called a *cluster*. We use the
28 http://www.corosync.org[Corosync Cluster Engine] for reliable group
29 communication, and such clusters can consist of up to 32 physical nodes
30 (probably more, dependent on network latency).
32 `pvecm` can be used to create a new cluster, join nodes to a cluster,
33 leave the cluster, get status information and do various other cluster
34 related tasks. The **P**rox**m**o**x** **C**luster **F**ile **S**ystem (``pmxcfs'')
35 is used to transparently distribute the cluster configuration to all cluster
38 Grouping nodes into a cluster has the following advantages:
40 * Centralized, web based management
42 * Multi-master clusters: each node can do all management task
44 * `pmxcfs`: database-driven file system for storing configuration files,
45 replicated in real-time on all nodes using `corosync`.
47 * Easy migration of virtual machines and containers between physical
52 * Cluster-wide services like firewall and HA
58 * All nodes must be in the same network as `corosync` uses IP Multicast
59 to communicate between nodes (also see
60 http://www.corosync.org[Corosync Cluster Engine]). Corosync uses UDP
61 ports 5404 and 5405 for cluster communication.
63 NOTE: Some switches do not support IP multicast by default and must be
64 manually enabled first.
66 * Date and time have to be synchronized.
68 * SSH tunnel on TCP port 22 between nodes is used.
70 * If you are interested in High Availability, you need to have at
71 least three nodes for reliable quorum. All nodes should have the
74 * We recommend a dedicated NIC for the cluster traffic, especially if
75 you use shared storage.
77 NOTE: It is not possible to mix Proxmox VE 3.x and earlier with
78 Proxmox VE 4.0 cluster nodes.
84 First, install {PVE} on all nodes. Make sure that each node is
85 installed with the final hostname and IP configuration. Changing the
86 hostname and IP is not possible after cluster creation.
88 Currently the cluster creation has to be done on the console, so you
89 need to login via `ssh`.
94 Login via `ssh` to the first {pve} node. Use a unique name for your cluster.
95 This name cannot be changed later.
97 hp1# pvecm create YOUR-CLUSTER-NAME
99 CAUTION: The cluster name is used to compute the default multicast
100 address. Please use unique cluster names if you run more than one
101 cluster inside your network.
103 To check the state of your cluster use:
108 Adding Nodes to the Cluster
109 ---------------------------
111 Login via `ssh` to the node you want to add.
113 hp2# pvecm add IP-ADDRESS-CLUSTER
115 For `IP-ADDRESS-CLUSTER` use the IP from an existing cluster node.
117 CAUTION: A new node cannot hold any VMs, because you would get
118 conflicts about identical VM IDs. Also, all existing configuration in
119 `/etc/pve` is overwritten when you join a new node to the cluster. To
120 workaround, use `vzdump` to backup and restore to a different VMID after
121 adding the node to the cluster.
123 To check the state of cluster:
127 .Cluster status after adding 4 nodes
132 Date: Mon Apr 20 12:30:13 2015
133 Quorum provider: corosync_votequorum
139 Votequorum information
140 ~~~~~~~~~~~~~~~~~~~~~~
147 Membership information
148 ~~~~~~~~~~~~~~~~~~~~~~
150 0x00000001 1 192.168.15.91
151 0x00000002 1 192.168.15.92 (local)
152 0x00000003 1 192.168.15.93
153 0x00000004 1 192.168.15.94
156 If you only want the list of all nodes use:
160 .List nodes in a cluster
164 Membership information
165 ~~~~~~~~~~~~~~~~~~~~~~
173 Adding Nodes With Separated Cluster Network
174 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
176 When adding a node to a cluster with a separated cluster network you need to
177 use the 'ringX_addr' parameters to set the nodes address on those networks:
181 pvecm add IP-ADDRESS-CLUSTER -ring0_addr IP-ADDRESS-RING0
184 If you want to use the Redundant Ring Protocol you will also want to pass the
185 'ring1_addr' parameter.
188 Remove a Cluster Node
189 ---------------------
191 CAUTION: Read carefully the procedure before proceeding, as it could
192 not be what you want or need.
194 Move all virtual machines from the node. Make sure you have no local
195 data or backups you want to keep, or save them accordingly.
196 In the following example we will remove the node hp4 from the cluster.
198 Log in to a *different* cluster node (not hp4), and issue a `pvecm nodes`
199 command to identify the node ID to remove:
204 Membership information
205 ~~~~~~~~~~~~~~~~~~~~~~
214 At this point you must power off hp4 and
215 make sure that it will not power on again (in the network) as it
218 IMPORTANT: As said above, it is critical to power off the node
219 *before* removal, and make sure that it will *never* power on again
220 (in the existing cluster network) as it is.
221 If you power on the node as it is, your cluster will be screwed up and
222 it could be difficult to restore a clean cluster state.
224 After powering off the node hp4, we can safely remove it from the cluster.
226 hp1# pvecm delnode hp4
228 If the operation succeeds no output is returned, just check the node
229 list again with `pvecm nodes` or `pvecm status`. You should see
237 Date: Mon Apr 20 12:44:28 2015
238 Quorum provider: corosync_votequorum
244 Votequorum information
245 ~~~~~~~~~~~~~~~~~~~~~~
252 Membership information
253 ~~~~~~~~~~~~~~~~~~~~~~
255 0x00000001 1 192.168.15.90 (local)
256 0x00000002 1 192.168.15.91
257 0x00000003 1 192.168.15.92
260 If, for whatever reason, you want that this server joins the same
261 cluster again, you have to
263 * reinstall {pve} on it from scratch
265 * then join it, as explained in the previous section.
267 [[pvecm_separate_node_without_reinstall]]
268 Separate A Node Without Reinstalling
269 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
271 CAUTION: This is *not* the recommended method, proceed with caution. Use the
272 above mentioned method if you're unsure.
274 You can also separate a node from a cluster without reinstalling it from
275 scratch. But after removing the node from the cluster it will still have
276 access to the shared storages! This must be resolved before you start removing
277 the node from the cluster. A {pve} cluster cannot share the exact same
278 storage with another cluster, as storage locking doesn't work over cluster
279 boundary. Further, it may also lead to VMID conflicts.
281 Its suggested that you create a new storage where only the node which you want
282 to separate has access. This can be an new export on your NFS or a new Ceph
283 pool, to name a few examples. Its just important that the exact same storage
284 does not gets accessed by multiple clusters. After setting this storage up move
285 all data from the node and its VMs to it. Then you are ready to separate the
286 node from the cluster.
288 WARNING: Ensure all shared resources are cleanly separated! You will run into
289 conflicts and problems else.
291 First stop the corosync and the pve-cluster services on the node:
294 systemctl stop pve-cluster
295 systemctl stop corosync
298 Start the cluster filesystem again in local mode:
304 Delete the corosync configuration files:
307 rm /etc/pve/corosync.conf
311 You can now start the filesystem again as normal service:
315 systemctl start pve-cluster
318 The node is now separated from the cluster. You can deleted it from a remaining
319 node of the cluster with:
322 pvecm delnode oldnode
325 If the command failed, because the remaining node in the cluster lost quorum
326 when the now separate node exited, you may set the expected votes to 1 as a workaround:
332 And the repeat the 'pvecm delnode' command.
334 Now switch back to the separated node, here delete all remaining files left
335 from the old cluster. This ensures that the node can be added to another
336 cluster again without problems.
340 rm /var/lib/corosync/*
343 As the configuration files from the other nodes are still in the cluster
344 filesystem you may want to clean those up too. Remove simply the whole
345 directory recursive from '/etc/pve/nodes/NODENAME', but check three times that
346 you used the correct one before deleting it.
348 CAUTION: The nodes SSH keys are still in the 'authorized_key' file, this means
349 the nodes can still connect to each other with public key authentication. This
350 should be fixed by removing the respective keys from the
351 '/etc/pve/priv/authorized_keys' file.
356 {pve} use a quorum-based technique to provide a consistent state among
359 [quote, from Wikipedia, Quorum (distributed computing)]
361 A quorum is the minimum number of votes that a distributed transaction
362 has to obtain in order to be allowed to perform an operation in a
366 In case of network partitioning, state changes requires that a
367 majority of nodes are online. The cluster switches to read-only mode
370 NOTE: {pve} assigns a single vote to each node by default.
375 The cluster network is the core of a cluster. All messages sent over it have to
376 be delivered reliable to all nodes in their respective order. In {pve} this
377 part is done by corosync, an implementation of a high performance low overhead
378 high availability development toolkit. It serves our decentralized
379 configuration file system (`pmxcfs`).
381 [[cluster-network-requirements]]
384 This needs a reliable network with latencies under 2 milliseconds (LAN
385 performance) to work properly. While corosync can also use unicast for
386 communication between nodes its **highly recommended** to have a multicast
387 capable network. The network should not be used heavily by other members,
388 ideally corosync runs on its own network.
389 *never* share it with network where storage communicates too.
391 Before setting up a cluster it is good practice to check if the network is fit
394 * Ensure that all nodes are in the same subnet. This must only be true for the
395 network interfaces used for cluster communication (corosync).
397 * Ensure all nodes can reach each other over those interfaces, using `ping` is
398 enough for a basic test.
400 * Ensure that multicast works in general and a high package rates. This can be
401 done with the `omping` tool. The final "%loss" number should be < 1%.
405 omping -c 10000 -i 0.001 -F -q NODE1-IP NODE2-IP ...
408 * Ensure that multicast communication works over an extended period of time.
409 This uncovers problems where IGMP snooping is activated on the network but
410 no multicast querier is active. This test has a duration of around 10
415 omping -c 600 -i 1 -q NODE1-IP NODE2-IP ...
418 Your network is not ready for clustering if any of these test fails. Recheck
419 your network configuration. Especially switches are notorious for having
420 multicast disabled by default or IGMP snooping enabled with no IGMP querier
423 In smaller cluster its also an option to use unicast if you really cannot get
426 Separate Cluster Network
427 ~~~~~~~~~~~~~~~~~~~~~~~~
429 When creating a cluster without any parameters the cluster network is generally
430 shared with the Web UI and the VMs and its traffic. Depending on your setup
431 even storage traffic may get sent over the same network. Its recommended to
432 change that, as corosync is a time critical real time application.
434 Setting Up A New Network
435 ^^^^^^^^^^^^^^^^^^^^^^^^
437 First you have to setup a new network interface. It should be on a physical
438 separate network. Ensure that your network fulfills the
439 <<cluster-network-requirements,cluster network requirements>>.
441 Separate On Cluster Creation
442 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
444 This is possible through the 'ring0_addr' and 'bindnet0_addr' parameter of
445 the 'pvecm create' command used for creating a new cluster.
447 If you have setup an additional NIC with a static address on 10.10.10.1/25
448 and want to send and receive all cluster communication over this interface
453 pvecm create test --ring0_addr 10.10.10.1 --bindnet0_addr 10.10.10.0
456 To check if everything is working properly execute:
459 systemctl status corosync
462 [[separate-cluster-net-after-creation]]
463 Separate After Cluster Creation
464 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
466 You can do this also if you have already created a cluster and want to switch
467 its communication to another network, without rebuilding the whole cluster.
468 This change may lead to short durations of quorum loss in the cluster, as nodes
469 have to restart corosync and come up one after the other on the new network.
471 Check how to <<edit-corosync-conf,edit the corosync.conf file>> first.
472 The open it and you should see a file similar to:
506 provider: corosync_votequorum
510 cluster_name: thomas-testcluster
516 bindnetaddr: 192.168.30.50
523 The first you want to do is add the 'name' properties in the node entries if
524 you do not see them already. Those *must* match the node name.
526 Then replace the address from the 'ring0_addr' properties with the new
527 addresses. You may use plain IP addresses or also hostnames here. If you use
528 hostnames ensure that they are resolvable from all nodes.
530 In my example I want to switch my cluster communication to the 10.10.10.1/25
531 network. So I replace all 'ring0_addr' respectively. I also set the bindnetaddr
532 in the totem section of the config to an address of the new network. It can be
533 any address from the subnet configured on the new network interface.
535 After you increased the 'config_version' property the new configuration file
551 ring0_addr: 10.10.10.2
558 ring0_addr: 10.10.10.3
565 ring0_addr: 10.10.10.1
571 provider: corosync_votequorum
575 cluster_name: thomas-testcluster
581 bindnetaddr: 10.10.10.1
588 Now after a final check whether all changed information is correct we save it
589 and see again the <<edit-corosync-conf,edit corosync.conf file>> section to
590 learn how to bring it in effect.
592 As our change cannot be enforced live from corosync we have to do an restart.
594 On a single node execute:
597 systemctl restart corosync
600 Now check if everything is fine:
604 systemctl status corosync
607 If corosync runs again correct restart corosync also on all other nodes.
608 They will then join the cluster membership one by one on the new network.
610 Redundant Ring Protocol
611 ~~~~~~~~~~~~~~~~~~~~~~~
612 To avoid a single point of failure you should implement counter measurements.
613 This can be on the hardware and operating system level through network bonding.
615 Corosync itself offers also a possibility to add redundancy through the so
616 called 'Redundant Ring Protocol'. This protocol allows running a second totem
617 ring on another network, this network should be physically separated from the
618 other rings network to actually increase availability.
620 RRP On Cluster Creation
621 ~~~~~~~~~~~~~~~~~~~~~~~
623 The 'pvecm create' command provides the additional parameters 'bindnetX_addr',
624 'ringX_addr' and 'rrp_mode', can be used for RRP configuration.
626 NOTE: See the <<corosync-conf-glossary,glossary>> if you do not know what each parameter means.
628 So if you have two networks, one on the 10.10.10.1/24 and the other on the
629 10.10.20.1/24 subnet you would execute:
633 pvecm create CLUSTERNAME -bindnet0_addr 10.10.10.1 -ring0_addr 10.10.10.1 \
634 -bindnet1_addr 10.10.20.1 -ring1_addr 10.10.20.1
637 RRP On Existing Clusters
638 ~~~~~~~~~~~~~~~~~~~~~~~~
640 You will take similar steps as described in
641 <<separate-cluster-net-after-creation,separating the cluster network>> to
642 enable RRP on an already running cluster. The single difference is, that you
643 will add `ring1` and use it instead of `ring0`.
645 First add a new `interface` subsection in the `totem` section, set its
646 `ringnumber` property to `1`. Set the interfaces `bindnetaddr` property to an
647 address of the subnet you have configured for your new ring.
648 Further set the `rrp_mode` to `passive`, this is the only stable mode.
650 Then add to each node entry in the `nodelist` section its new `ring1_addr`
651 property with the nodes additional ring address.
653 So if you have two networks, one on the 10.10.10.1/24 and the other on the
654 10.10.20.1/24 subnet, the final configuration file should look like:
665 bindnetaddr: 10.10.10.1
669 bindnetaddr: 10.10.20.1
679 ring0_addr: 10.10.10.1
680 ring1_addr: 10.10.20.1
687 ring0_addr: 10.10.10.2
688 ring1_addr: 10.10.20.2
691 [...] # other cluster nodes here
694 [...] # other remaining config sections here
698 Bring it in effect like described in the
699 <<edit-corosync-conf,edit the corosync.conf file>> section.
701 This is a change which cannot take live in effect and needs at least a restart
702 of corosync. Recommended is a restart of the whole cluster.
704 If you cannot reboot the whole cluster ensure no High Availability services are
705 configured and the stop the corosync service on all nodes. After corosync is
706 stopped on all nodes start it one after the other again.
708 Corosync Configuration
709 ----------------------
711 The `/etc/pve/corosync.conf` file plays a central role in {pve} cluster. It
712 controls the cluster member ship and its network.
713 For reading more about it check the corosync.conf man page:
719 For node membership you should always use the `pvecm` tool provided by {pve}.
720 You may have to edit the configuration file manually for other changes.
721 Here are a few best practice tips for doing this.
723 [[edit-corosync-conf]]
727 Editing the corosync.conf file can be not always straight forward. There are
728 two on each cluster, one in `/etc/pve/corosync.conf` and the other in
729 `/etc/corosync/corosync.conf`. Editing the one in our cluster file system will
730 propagate the changes to the local one, but not vice versa.
732 The configuration will get updated automatically as soon as the file changes.
733 This means changes which can be integrated in a running corosync will take
734 instantly effect. So you should always make a copy and edit that instead, to
735 avoid triggering some unwanted changes by an in between safe.
739 cp /etc/pve/corosync.conf /etc/pve/corosync.conf.new
742 Then open the Config file with your favorite editor, `nano` and `vim.tiny` are
743 preinstalled on {pve} for example.
745 NOTE: Always increment the 'config_version' number on configuration changes,
746 omitting this can lead to problems.
748 After making the necessary changes create another copy of the current working
749 configuration file. This serves as a backup if the new configuration fails to
750 apply or makes problems in other ways.
754 cp /etc/pve/corosync.conf /etc/pve/corosync.conf.bak
757 Then move the new configuration file over the old one:
760 mv /etc/pve/corosync.conf.new /etc/pve/corosync.conf
763 You may check with the commands
766 systemctl status corosync
767 journalctl -b -u corosync
770 If the change could applied automatically. If not you may have to restart the
771 corosync service via:
774 systemctl restart corosync
777 On errors check the troubleshooting section below.
782 Issue: 'quorum.expected_votes must be configured'
783 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
785 When corosync starts to fail and you get the following message in the system log:
789 corosync[1647]: [QUORUM] Quorum provider: corosync_votequorum failed to initialize.
790 corosync[1647]: [SERV ] Service engine 'corosync_quorum' failed to load for reason
791 'configuration error: nodelist or quorum.expected_votes must be configured!'
795 It means that the hostname you set for corosync 'ringX_addr' in the
796 configuration could not be resolved.
799 Write Configuration When Not Quorate
800 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
802 If you need to change '/etc/pve/corosync.conf' on an node with no quorum, and you
803 know what you do, use:
809 This sets the expected vote count to 1 and makes the cluster quorate. You can
810 now fix your configuration, or revert it back to the last working backup.
812 This is not enough if corosync cannot start anymore. Here its best to edit the
813 local copy of the corosync configuration in '/etc/corosync/corosync.conf' so
814 that corosync can start again. Ensure that on all nodes this configuration has
815 the same content to avoid split brains. If you are not sure what went wrong
816 it's best to ask the Proxmox Community to help you.
819 [[corosync-conf-glossary]]
820 Corosync Configuration Glossary
821 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
824 This names the different ring addresses for the corosync totem rings used for
825 the cluster communication.
828 Defines to which interface the ring should bind to. It may be any address of
829 the subnet configured on the interface we want to use. In general its the
830 recommended to just use an address a node uses on this interface.
833 Specifies the mode of the redundant ring protocol and may be passive, active or
834 none. Note that use of active is highly experimental and not official
835 supported. Passive is the preferred mode, it may double the cluster
836 communication throughput and increases availability.
842 It is obvious that a cluster is not quorate when all nodes are
843 offline. This is a common case after a power failure.
845 NOTE: It is always a good idea to use an uninterruptible power supply
846 (``UPS'', also called ``battery backup'') to avoid this state, especially if
849 On node startup, the `pve-guests` service is started and waits for
850 quorum. Once quorate, it starts all guests which have the `onboot`
853 When you turn on nodes, or when power comes back after power failure,
854 it is likely that some nodes boots faster than others. Please keep in
855 mind that guest startup is delayed until you reach quorum.
861 Migrating virtual guests to other nodes is a useful feature in a
862 cluster. There are settings to control the behavior of such
863 migrations. This can be done via the configuration file
864 `datacenter.cfg` or for a specific migration via API or command line
867 It makes a difference if a Guest is online or offline, or if it has
868 local resources (like a local disk).
870 For Details about Virtual Machine Migration see the
871 xref:qm_migration[QEMU/KVM Migration Chapter]
873 For Details about Container Migration see the
874 xref:pct_migration[Container Migration Chapter]
879 The migration type defines if the migration data should be sent over an
880 encrypted (`secure`) channel or an unencrypted (`insecure`) one.
881 Setting the migration type to insecure means that the RAM content of a
882 virtual guest gets also transferred unencrypted, which can lead to
883 information disclosure of critical data from inside the guest (for
884 example passwords or encryption keys).
886 Therefore, we strongly recommend using the secure channel if you do
887 not have full control over the network and can not guarantee that no
888 one is eavesdropping to it.
890 NOTE: Storage migration does not follow this setting. Currently, it
891 always sends the storage content over a secure channel.
893 Encryption requires a lot of computing power, so this setting is often
894 changed to "unsafe" to achieve better performance. The impact on
895 modern systems is lower because they implement AES encryption in
896 hardware. The performance impact is particularly evident in fast
897 networks where you can transfer 10 Gbps or more.
903 By default, {pve} uses the network in which cluster communication
904 takes place to send the migration traffic. This is not optimal because
905 sensitive cluster traffic can be disrupted and this network may not
906 have the best bandwidth available on the node.
908 Setting the migration network parameter allows the use of a dedicated
909 network for the entire migration traffic. In addition to the memory,
910 this also affects the storage traffic for offline migrations.
912 The migration network is set as a network in the CIDR notation. This
913 has the advantage that you do not have to set individual IP addresses
914 for each node. {pve} can determine the real address on the
915 destination node from the network specified in the CIDR form. To
916 enable this, the network must be specified so that each node has one,
917 but only one IP in the respective network.
923 We assume that we have a three-node setup with three separate
924 networks. One for public communication with the Internet, one for
925 cluster communication and a very fast one, which we want to use as a
926 dedicated network for migration.
928 A network configuration for such a setup might look as follows:
931 iface eno1 inet manual
935 iface vmbr0 inet static
937 netmask 255.255.250.0
945 iface eno2 inet static
947 netmask 255.255.255.0
951 iface eno3 inet static
953 netmask 255.255.255.0
956 Here, we will use the network 10.1.2.0/24 as a migration network. For
957 a single migration, you can do this using the `migration_network`
958 parameter of the command line tool:
961 # qm migrate 106 tre --online --migration_network 10.1.2.0/24
964 To configure this as the default network for all migrations in the
965 cluster, set the `migration` property of the `/etc/pve/datacenter.cfg`
969 # use dedicated migration network
970 migration: secure,network=10.1.2.0/24
973 NOTE: The migration type must always be set when the migration network
974 gets set in `/etc/pve/datacenter.cfg`.
978 include::pve-copyright.adoc[]