4 include::attributes.txt[]
10 pvecm - Proxmox VE Cluster Manager
15 include::pvecm.1-synopsis.adoc[]
24 include::attributes.txt[]
30 The {PVE} cluster manager `pvecm` is a tool to create a group of
31 physical servers. Such a group is called a *cluster*. We use the
32 http://www.corosync.org[Corosync Cluster Engine] for reliable group
33 communication, and such clusters can consist of up to 32 physical nodes
34 (probably more, dependent on network latency).
36 `pvecm` can be used to create a new cluster, join nodes to a cluster,
37 leave the cluster, get status information and do various other cluster
38 related tasks. The **P**rox**m**o**x** **C**luster **F**ile **S**ystem (``pmxcfs'')
39 is used to transparently distribute the cluster configuration to all cluster
42 Grouping nodes into a cluster has the following advantages:
44 * Centralized, web based management
46 * Multi-master clusters: each node can do all management task
48 * `pmxcfs`: database-driven file system for storing configuration files,
49 replicated in real-time on all nodes using `corosync`.
51 * Easy migration of virtual machines and containers between physical
56 * Cluster-wide services like firewall and HA
62 * All nodes must be in the same network as `corosync` uses IP Multicast
63 to communicate between nodes (also see
64 http://www.corosync.org[Corosync Cluster Engine]). Corosync uses UDP
65 ports 5404 and 5405 for cluster communication.
67 NOTE: Some switches do not support IP multicast by default and must be
68 manually enabled first.
70 * Date and time have to be synchronized.
72 * SSH tunnel on TCP port 22 between nodes is used.
74 * If you are interested in High Availability, you need to have at
75 least three nodes for reliable quorum. All nodes should have the
78 * We recommend a dedicated NIC for the cluster traffic, especially if
79 you use shared storage.
81 NOTE: It is not possible to mix Proxmox VE 3.x and earlier with
82 Proxmox VE 4.0 cluster nodes.
88 First, install {PVE} on all nodes. Make sure that each node is
89 installed with the final hostname and IP configuration. Changing the
90 hostname and IP is not possible after cluster creation.
92 Currently the cluster creation has to be done on the console, so you
93 need to login via `ssh`.
98 Login via `ssh` to the first {pve} node. Use a unique name for your cluster.
99 This name cannot be changed later.
101 hp1# pvecm create YOUR-CLUSTER-NAME
103 CAUTION: The cluster name is used to compute the default multicast
104 address. Please use unique cluster names if you run more than one
105 cluster inside your network.
107 To check the state of your cluster use:
112 Adding Nodes to the Cluster
113 ---------------------------
115 Login via `ssh` to the node you want to add.
117 hp2# pvecm add IP-ADDRESS-CLUSTER
119 For `IP-ADDRESS-CLUSTER` use the IP from an existing cluster node.
121 CAUTION: A new node cannot hold any VMs, because you would get
122 conflicts about identical VM IDs. Also, all existing configuration in
123 `/etc/pve` is overwritten when you join a new node to the cluster. To
124 workaround, use `vzdump` to backup and restore to a different VMID after
125 adding the node to the cluster.
127 To check the state of cluster:
131 .Cluster status after adding 4 nodes
136 Date: Mon Apr 20 12:30:13 2015
137 Quorum provider: corosync_votequorum
143 Votequorum information
144 ~~~~~~~~~~~~~~~~~~~~~~
151 Membership information
152 ~~~~~~~~~~~~~~~~~~~~~~
154 0x00000001 1 192.168.15.91
155 0x00000002 1 192.168.15.92 (local)
156 0x00000003 1 192.168.15.93
157 0x00000004 1 192.168.15.94
160 If you only want the list of all nodes use:
164 .List nodes in a cluster
168 Membership information
169 ~~~~~~~~~~~~~~~~~~~~~~
177 Adding Nodes With Separated Cluster Network
178 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
180 When adding a node to a cluster with a separated cluster network you need to
181 use the 'ringX_addr' parameters to set the nodes address on those networks:
185 pvecm add IP-ADDRESS-CLUSTER -ring0_addr IP-ADDRESS-RING0
188 If you want to use the Redundant Ring Protocol you will also want to pass the
189 'ring1_addr' parameter.
192 Remove a Cluster Node
193 ---------------------
195 CAUTION: Read carefully the procedure before proceeding, as it could
196 not be what you want or need.
198 Move all virtual machines from the node. Make sure you have no local
199 data or backups you want to keep, or save them accordingly.
201 Log in to one remaining node via ssh. Issue a `pvecm nodes` command to
202 identify the node ID:
209 Date: Mon Apr 20 12:30:13 2015
210 Quorum provider: corosync_votequorum
216 Votequorum information
217 ~~~~~~~~~~~~~~~~~~~~~~
224 Membership information
225 ~~~~~~~~~~~~~~~~~~~~~~
227 0x00000001 1 192.168.15.91 (local)
228 0x00000002 1 192.168.15.92
229 0x00000003 1 192.168.15.93
230 0x00000004 1 192.168.15.94
233 IMPORTANT: at this point you must power off the node to be removed and
234 make sure that it will not power on again (in the network) as it
240 Membership information
241 ~~~~~~~~~~~~~~~~~~~~~~
249 Log in to one remaining node via ssh. Issue the delete command (here
250 deleting node `hp4`):
252 hp1# pvecm delnode hp4
254 If the operation succeeds no output is returned, just check the node
255 list again with `pvecm nodes` or `pvecm status`. You should see
263 Date: Mon Apr 20 12:44:28 2015
264 Quorum provider: corosync_votequorum
270 Votequorum information
271 ~~~~~~~~~~~~~~~~~~~~~~
278 Membership information
279 ~~~~~~~~~~~~~~~~~~~~~~
281 0x00000001 1 192.168.15.90 (local)
282 0x00000002 1 192.168.15.91
283 0x00000003 1 192.168.15.92
286 IMPORTANT: as said above, it is very important to power off the node
287 *before* removal, and make sure that it will *never* power on again
288 (in the existing cluster network) as it is.
290 If you power on the node as it is, your cluster will be screwed up and
291 it could be difficult to restore a clean cluster state.
293 If, for whatever reason, you want that this server joins the same
294 cluster again, you have to
296 * reinstall {pve} on it from scratch
298 * then join it, as explained in the previous section.
300 Separate A Node Without Reinstalling
301 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
303 CAUTION: This is *not* the recommended method, proceed with caution. Use the
304 above mentioned method if you're unsure.
306 You can also separate a node from a cluster without reinstalling it from
307 scratch. But after removing the node from the cluster it will still have
308 access to the shared storages! This must be resolved before you start removing
309 the node from the cluster. A {pve} cluster cannot share the exact same
310 storage with another cluster, as it leads to VMID conflicts.
312 Its suggested that you create a new storage where only the node which you want
313 to separate has access. This can be an new export on your NFS or a new Ceph
314 pool, to name a few examples. Its just important that the exact same storage
315 does not gets accessed by multiple clusters. After setting this storage up move
316 all data from the node and its VMs to it. Then you are ready to separate the
317 node from the cluster.
319 WARNING: Ensure all shared resources are cleanly separated! You will run into
320 conflicts and problems else.
322 First stop the corosync and the pve-cluster services on the node:
325 systemctl stop pve-cluster
326 systemctl stop corosync
329 Start the cluster filesystem again in local mode:
335 Delete the corosync configuration files:
338 rm /etc/pve/corosync.conf
342 You can now start the filesystem again as normal service:
346 systemctl start pve-cluster
349 The node is now separated from the cluster. You can deleted it from a remaining
350 node of the cluster with:
353 pvecm delnode oldnode
356 If the command failed, because the remaining node in the cluster lost quorum
357 when the now separate node exited, you may set the expected votes to 1 as a workaround:
363 And the repeat the 'pvecm delnode' command.
365 Now switch back to the separated node, here delete all remaining files left
366 from the old cluster. This ensures that the node can be added to another
367 cluster again without problems.
371 rm /var/lib/corosync/*
374 As the configuration files from the other nodes are still in the cluster
375 filesystem you may want to clean those up too. Remove simply the whole
376 directory recursive from '/etc/pve/nodes/NODENAME', but check three times that
377 you used the correct one before deleting it.
379 CAUTION: The nodes SSH keys are still in the 'authorized_key' file, this means
380 the nodes can still connect to each other with public key authentication. This
381 should be fixed by removing the respective keys from the
382 '/etc/pve/priv/authorized_keys' file.
387 {pve} use a quorum-based technique to provide a consistent state among
390 [quote, from Wikipedia, Quorum (distributed computing)]
392 A quorum is the minimum number of votes that a distributed transaction
393 has to obtain in order to be allowed to perform an operation in a
397 In case of network partitioning, state changes requires that a
398 majority of nodes are online. The cluster switches to read-only mode
401 NOTE: {pve} assigns a single vote to each node by default.
406 The cluster network is the core of a cluster. All messages sent over it have to
407 be delivered reliable to all nodes in their respective order. In {pve} this
408 part is done by corosync, an implementation of a high performance low overhead
409 high availability development toolkit. It serves our decentralized
410 configuration file system (`pmxcfs`).
412 [[cluster-network-requirements]]
415 This needs a reliable network with latencies under 2 milliseconds (LAN
416 performance) to work properly. While corosync can also use unicast for
417 communication between nodes its **highly recommended** to have a multicast
418 capable network. The network should not be used heavily by other members,
419 ideally corosync runs on its own network.
420 *never* share it with network where storage communicates too.
422 Before setting up a cluster it is good practice to check if the network is fit
425 * Ensure that all nodes are in the same subnet. This must only be true for the
426 network interfaces used for cluster communication (corosync).
428 * Ensure all nodes can reach each other over those interfaces, using `ping` is
429 enough for a basic test.
431 * Ensure that multicast works in general and a high package rates. This can be
432 done with the `omping` tool. The final "%loss" number should be < 1%.
435 omping -c 10000 -i 0.001 -F -q NODE1-IP NODE2-IP ...
438 * Ensure that multicast communication works over an extended period of time.
439 This covers up problems where IGMP snooping is activated on the network but
440 no multicast querier is active. This test has a duration of around 10
444 omping -c 600 -i 1 -q NODE1-IP NODE2-IP ...
447 Your network is not ready for clustering if any of these test fails. Recheck
448 your network configuration. Especially switches are notorious for having
449 multicast disabled by default or IGMP snooping enabled with no IGMP querier
452 In smaller cluster its also an option to use unicast if you really cannot get
455 Separate Cluster Network
456 ~~~~~~~~~~~~~~~~~~~~~~~~
458 When creating a cluster without any parameters the cluster network is generally
459 shared with the Web UI and the VMs and its traffic. Depending on your setup
460 even storage traffic may get sent over the same network. Its recommended to
461 change that, as corosync is a time critical real time application.
463 Setting Up A New Network
464 ^^^^^^^^^^^^^^^^^^^^^^^^
466 First you have to setup a new network interface. It should be on a physical
467 separate network. Ensure that your network fulfills the
468 <<cluster-network-requirements,cluster network requirements>>.
470 Separate On Cluster Creation
471 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
473 This is possible through the 'ring0_addr' and 'bindnet0_addr' parameter of
474 the 'pvecm create' command used for creating a new cluster.
476 If you have setup a additional NIC with a static address on 10.10.10.1/25
477 and want to send and receive all cluster communication over this interface
482 pvecm create test --ring0_addr 10.10.10.1 --bindnet0_addr 10.10.10.0
485 To check if everything is working properly execute:
488 systemctl status corosync
491 [[separate-cluster-net-after-creation]]
492 Separate After Cluster Creation
493 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
495 You can do this also if you have already created a cluster and want to switch
496 its communication to another network, without rebuilding the whole cluster.
497 This change may lead to short durations of quorum loss in the cluster, as nodes
498 have to restart corosync and come up one after the other on the new network.
500 Check how to <<edit-corosync-conf,edit the corosync.conf file>> first.
501 The open it and you should see a file similar to:
535 provider: corosync_votequorum
539 cluster_name: thomas-testcluster
545 bindnetaddr: 192.168.30.50
552 The first you want to do is add the 'name' properties in the node entries if
553 you do not see them already. Those *must* match the node name.
555 Then replace the address from the 'ring0_addr' properties with the new
556 addresses. You may use plain IP addresses or also hostnames here. If you use
557 hostnames ensure that they are resolvable from all nodes.
559 In my example I want to switch my cluster communication to the 10.10.10.1/25
560 network. So I replace all 'ring0_addr' respectively. I also set the bindetaddr
561 in the totem section of the config to an address of the new network. It can be
562 any address from the subnet configured on the new network interface.
564 After you increased the 'config_version' property the new configuration file
580 ring0_addr: 10.10.10.2
587 ring0_addr: 10.10.10.3
594 ring0_addr: 10.10.10.1
600 provider: corosync_votequorum
604 cluster_name: thomas-testcluster
610 bindnetaddr: 10.10.10.1
617 Now after a final check whether all changed information is correct we save it
618 and see again the <<edit-corosync-conf,edit corosync.conf file>> section to
619 learn how to bring it in effect.
621 As our change cannot be enforced live from corosync we have to do an restart.
623 On a single node execute:
626 systemctl restart corosync
629 Now check if everything is fine:
633 systemctl status corosync
636 If corosync runs again correct restart corosync also on all other nodes.
637 They will then join the cluster membership one by one on the new network.
639 Redundant Ring Protocol
640 ~~~~~~~~~~~~~~~~~~~~~~~
641 To avoid a single point of failure you should implement counter measurements.
642 This can be on the hardware and operating system level through network bonding.
644 Corosync itself offers also a possibility to add redundancy through the so
645 called 'Redundant Ring Protocol'. This protocol allows running a second totem
646 ring on another network, this network should be physically separated from the
647 other rings network to actually increase availability.
649 RRP On Cluster Creation
650 ~~~~~~~~~~~~~~~~~~~~~~~
652 The 'pvecm create' command provides the additional parameters 'bindnetX_addr',
653 'ringX_addr' and 'rrp_mode', can be used for RRP configuration.
655 NOTE: See the <<corosync-conf-glossary,glossary>> if you do not know what each parameter means.
657 So if you have two networks, one on the 10.10.10.1/24 and the other on the
658 10.10.20.1/24 subnet you would execute:
662 pvecm create CLUSTERNAME -bindnet0_addr 10.10.10.1 -ring0_addr 10.10.10.1 \
663 -bindnet1_addr 10.10.20.1 -ring1_addr 10.10.20.1
666 RRP On A Created Cluster
667 ~~~~~~~~~~~~~~~~~~~~~~~~
669 When enabling an already running cluster to use RRP you will take similar steps
670 as describe in <<separate-cluster-net-after-creation,separating the cluster
671 network>>. You just do it on another ring.
673 First add a new `interface` subsection in the `totem` section, set its
674 `ringnumber` property to `1`. Set the interfaces `bindnetaddr` property to an
675 address of the subnet you have configured for your new ring.
676 Further set the `rrp_mode` to `passive`, this is the only stable mode.
678 Then add to each node entry in the `nodelist` section its new `ring1_addr`
679 property with the nodes additional ring address.
681 So if you have two networks, one on the 10.10.10.1/24 and the other on the
682 10.10.20.1/24 subnet, the final configuration file should look like:
693 bindnetaddr: 10.10.10.1
697 bindnetaddr: 10.10.20.1
707 ring0_addr: 10.10.10.1
708 ring1_addr: 10.10.20.1
715 ring0_addr: 10.10.10.2
716 ring1_addr: 10.10.20.2
719 [...] # other cluster nodes here
722 [...] # other remaining config sections here
726 Bring it in effect like described in the <<edit-corosync-conf,edit the
727 corosync.conf file>> section.
729 This is a change which cannot take live in effect and needs at least a restart
730 of corosync. Recommended is a restart of the whole cluster.
732 If you cannot reboot the whole cluster ensure no High Availability services are
733 configured and the stop the corosync service on all nodes. After corosync is
734 stopped on all nodes start it one after the other again.
736 Corosync Configuration
737 ----------------------
739 The `/ect/pve/corosync.conf` file plays a central role in {pve} cluster. It
740 controls the cluster member ship and its network.
741 For reading more about it check the corosync.conf man page:
747 For node membership you should always use the `pvecm` tool provided by {pve}.
748 You may have to edit the configuration file manually for other changes.
749 Here are a few best practice tips for doing this.
751 [[edit-corosync-conf]]
755 Editing the corosync.conf file can be not always straight forward. There are
756 two on each cluster, one in `/etc/pve/corosync.conf` and the other in
757 `/etc/corosync/corosync.conf`. Editing the one in our cluster file system will
758 propagate the changes to the local one, but not vice versa.
760 The configuration will get updated automatically as soon as the file changes.
761 This means changes which can be integrated in a running corosync will take
762 instantly effect. So you should always make a copy and edit that instead, to
763 avoid triggering some unwanted changes by an in between safe.
767 cp /etc/pve/corosync.conf /etc/pve/corosync.conf.new
770 Then open the Config file with your favorite editor, `nano` and `vim.tiny` are
771 preinstalled on {pve} for example.
773 NOTE: Always increment the 'config_version' number on configuration changes,
774 omitting this can lead to problems.
776 After making the necessary changes create another copy of the current working
777 configuration file. This serves as a backup if the new configuration fails to
778 apply or makes problems in other ways.
782 cp /etc/pve/corosync.conf /etc/pve/corosync.conf.bak
785 Then move the new configuration file over the old one:
788 mv /etc/pve/corosync.conf.new /etc/pve/corosync.conf
791 You may check with the commands
794 systemctl status corosync
795 journalctl -b -u corosync
798 If the change could applied automatically. If not you may have to restart the
799 corosync service via:
802 systemctl restart corosync
805 On errors check the troubleshooting section below.
810 Issue: 'quorum.expected_votes must be configured'
811 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
813 When corosync starts to fail and you get the following message in the system log:
817 corosync[1647]: [QUORUM] Quorum provider: corosync_votequorum failed to initialize.
818 corosync[1647]: [SERV ] Service engine 'corosync_quorum' failed to load for reason
819 'configuration error: nodelist or quorum.expected_votes must be configured!'
823 It means that the hostname you set for corosync 'ringX_addr' in the
824 configuration could not be resolved.
827 Write Configuration When Not Quorate
828 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
830 If you need to change '/etc/pve/corosync.conf' on an node with no quorum, and you
831 know what you do, use:
837 This sets the expected vote count to 1 and makes the cluster quorate. You can
838 now fix your configuration, or revert it back to the last working backup.
840 This is not enough if corosync cannot start anymore. Here its best to edit the
841 local copy of the corosync configuration in '/etc/corosync/corosync.conf' so
842 that corosync can start again. Ensure that on all nodes this configuration has
843 the same content to avoid split brains. If you are not sure what went wrong
844 it's best to ask the Proxmox Community to help you.
847 [[corosync-conf-glossary]]
848 Corosync Configuration Glossary
849 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
852 This names the different ring addresses for the corosync totem rings used for
853 the cluster communication.
856 Defines to which interface the ring should bind to. It may be any address of
857 the subnet configured on the interface we want to use. In general its the
858 recommended to just use an address a node uses on this interface.
861 Specifies the mode of the redundant ring protocol and may be passive, active or
862 none. Note that use of active is highly experimental and not official
863 supported. Passive is the preferred mode, it may double the cluster
864 communication throughput and increases availability.
870 It is obvious that a cluster is not quorate when all nodes are
871 offline. This is a common case after a power failure.
873 NOTE: It is always a good idea to use an uninterruptible power supply
874 (``UPS'', also called ``battery backup'') to avoid this state, especially if
877 On node startup, service `pve-manager` is started and waits for
878 quorum. Once quorate, it starts all guests which have the `onboot`
881 When you turn on nodes, or when power comes back after power failure,
882 it is likely that some nodes boots faster than others. Please keep in
883 mind that guest startup is delayed until you reach quorum.
887 include::pve-copyright.adoc[]