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.
197 Log in to one remaining node via ssh. Issue a `pvecm nodes` command to
198 identify the node ID:
205 Date: Mon Apr 20 12:30:13 2015
206 Quorum provider: corosync_votequorum
212 Votequorum information
213 ~~~~~~~~~~~~~~~~~~~~~~
220 Membership information
221 ~~~~~~~~~~~~~~~~~~~~~~
223 0x00000001 1 192.168.15.91 (local)
224 0x00000002 1 192.168.15.92
225 0x00000003 1 192.168.15.93
226 0x00000004 1 192.168.15.94
229 IMPORTANT: at this point you must power off the node to be removed and
230 make sure that it will not power on again (in the network) as it
236 Membership information
237 ~~~~~~~~~~~~~~~~~~~~~~
245 Log in to one remaining node via ssh. Issue the delete command (here
246 deleting node `hp4`):
248 hp1# pvecm delnode hp4
250 If the operation succeeds no output is returned, just check the node
251 list again with `pvecm nodes` or `pvecm status`. You should see
259 Date: Mon Apr 20 12:44:28 2015
260 Quorum provider: corosync_votequorum
266 Votequorum information
267 ~~~~~~~~~~~~~~~~~~~~~~
274 Membership information
275 ~~~~~~~~~~~~~~~~~~~~~~
277 0x00000001 1 192.168.15.90 (local)
278 0x00000002 1 192.168.15.91
279 0x00000003 1 192.168.15.92
282 IMPORTANT: as said above, it is very important to power off the node
283 *before* removal, and make sure that it will *never* power on again
284 (in the existing cluster network) as it is.
286 If you power on the node as it is, your cluster will be screwed up and
287 it could be difficult to restore a clean cluster state.
289 If, for whatever reason, you want that this server joins the same
290 cluster again, you have to
292 * reinstall {pve} on it from scratch
294 * then join it, as explained in the previous section.
296 [[pvecm_separate_node_without_reinstall]]
297 Separate A Node Without Reinstalling
298 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
300 CAUTION: This is *not* the recommended method, proceed with caution. Use the
301 above mentioned method if you're unsure.
303 You can also separate a node from a cluster without reinstalling it from
304 scratch. But after removing the node from the cluster it will still have
305 access to the shared storages! This must be resolved before you start removing
306 the node from the cluster. A {pve} cluster cannot share the exact same
307 storage with another cluster, as it leads to VMID conflicts.
309 Its suggested that you create a new storage where only the node which you want
310 to separate has access. This can be an new export on your NFS or a new Ceph
311 pool, to name a few examples. Its just important that the exact same storage
312 does not gets accessed by multiple clusters. After setting this storage up move
313 all data from the node and its VMs to it. Then you are ready to separate the
314 node from the cluster.
316 WARNING: Ensure all shared resources are cleanly separated! You will run into
317 conflicts and problems else.
319 First stop the corosync and the pve-cluster services on the node:
322 systemctl stop pve-cluster
323 systemctl stop corosync
326 Start the cluster filesystem again in local mode:
332 Delete the corosync configuration files:
335 rm /etc/pve/corosync.conf
339 You can now start the filesystem again as normal service:
343 systemctl start pve-cluster
346 The node is now separated from the cluster. You can deleted it from a remaining
347 node of the cluster with:
350 pvecm delnode oldnode
353 If the command failed, because the remaining node in the cluster lost quorum
354 when the now separate node exited, you may set the expected votes to 1 as a workaround:
360 And the repeat the 'pvecm delnode' command.
362 Now switch back to the separated node, here delete all remaining files left
363 from the old cluster. This ensures that the node can be added to another
364 cluster again without problems.
368 rm /var/lib/corosync/*
371 As the configuration files from the other nodes are still in the cluster
372 filesystem you may want to clean those up too. Remove simply the whole
373 directory recursive from '/etc/pve/nodes/NODENAME', but check three times that
374 you used the correct one before deleting it.
376 CAUTION: The nodes SSH keys are still in the 'authorized_key' file, this means
377 the nodes can still connect to each other with public key authentication. This
378 should be fixed by removing the respective keys from the
379 '/etc/pve/priv/authorized_keys' file.
384 {pve} use a quorum-based technique to provide a consistent state among
387 [quote, from Wikipedia, Quorum (distributed computing)]
389 A quorum is the minimum number of votes that a distributed transaction
390 has to obtain in order to be allowed to perform an operation in a
394 In case of network partitioning, state changes requires that a
395 majority of nodes are online. The cluster switches to read-only mode
398 NOTE: {pve} assigns a single vote to each node by default.
403 The cluster network is the core of a cluster. All messages sent over it have to
404 be delivered reliable to all nodes in their respective order. In {pve} this
405 part is done by corosync, an implementation of a high performance low overhead
406 high availability development toolkit. It serves our decentralized
407 configuration file system (`pmxcfs`).
409 [[cluster-network-requirements]]
412 This needs a reliable network with latencies under 2 milliseconds (LAN
413 performance) to work properly. While corosync can also use unicast for
414 communication between nodes its **highly recommended** to have a multicast
415 capable network. The network should not be used heavily by other members,
416 ideally corosync runs on its own network.
417 *never* share it with network where storage communicates too.
419 Before setting up a cluster it is good practice to check if the network is fit
422 * Ensure that all nodes are in the same subnet. This must only be true for the
423 network interfaces used for cluster communication (corosync).
425 * Ensure all nodes can reach each other over those interfaces, using `ping` is
426 enough for a basic test.
428 * Ensure that multicast works in general and a high package rates. This can be
429 done with the `omping` tool. The final "%loss" number should be < 1%.
432 omping -c 10000 -i 0.001 -F -q NODE1-IP NODE2-IP ...
435 * Ensure that multicast communication works over an extended period of time.
436 This covers up problems where IGMP snooping is activated on the network but
437 no multicast querier is active. This test has a duration of around 10
441 omping -c 600 -i 1 -q NODE1-IP NODE2-IP ...
444 Your network is not ready for clustering if any of these test fails. Recheck
445 your network configuration. Especially switches are notorious for having
446 multicast disabled by default or IGMP snooping enabled with no IGMP querier
449 In smaller cluster its also an option to use unicast if you really cannot get
452 Separate Cluster Network
453 ~~~~~~~~~~~~~~~~~~~~~~~~
455 When creating a cluster without any parameters the cluster network is generally
456 shared with the Web UI and the VMs and its traffic. Depending on your setup
457 even storage traffic may get sent over the same network. Its recommended to
458 change that, as corosync is a time critical real time application.
460 Setting Up A New Network
461 ^^^^^^^^^^^^^^^^^^^^^^^^
463 First you have to setup a new network interface. It should be on a physical
464 separate network. Ensure that your network fulfills the
465 <<cluster-network-requirements,cluster network requirements>>.
467 Separate On Cluster Creation
468 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
470 This is possible through the 'ring0_addr' and 'bindnet0_addr' parameter of
471 the 'pvecm create' command used for creating a new cluster.
473 If you have setup a additional NIC with a static address on 10.10.10.1/25
474 and want to send and receive all cluster communication over this interface
479 pvecm create test --ring0_addr 10.10.10.1 --bindnet0_addr 10.10.10.0
482 To check if everything is working properly execute:
485 systemctl status corosync
488 [[separate-cluster-net-after-creation]]
489 Separate After Cluster Creation
490 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
492 You can do this also if you have already created a cluster and want to switch
493 its communication to another network, without rebuilding the whole cluster.
494 This change may lead to short durations of quorum loss in the cluster, as nodes
495 have to restart corosync and come up one after the other on the new network.
497 Check how to <<edit-corosync-conf,edit the corosync.conf file>> first.
498 The open it and you should see a file similar to:
532 provider: corosync_votequorum
536 cluster_name: thomas-testcluster
542 bindnetaddr: 192.168.30.50
549 The first you want to do is add the 'name' properties in the node entries if
550 you do not see them already. Those *must* match the node name.
552 Then replace the address from the 'ring0_addr' properties with the new
553 addresses. You may use plain IP addresses or also hostnames here. If you use
554 hostnames ensure that they are resolvable from all nodes.
556 In my example I want to switch my cluster communication to the 10.10.10.1/25
557 network. So I replace all 'ring0_addr' respectively. I also set the bindetaddr
558 in the totem section of the config to an address of the new network. It can be
559 any address from the subnet configured on the new network interface.
561 After you increased the 'config_version' property the new configuration file
577 ring0_addr: 10.10.10.2
584 ring0_addr: 10.10.10.3
591 ring0_addr: 10.10.10.1
597 provider: corosync_votequorum
601 cluster_name: thomas-testcluster
607 bindnetaddr: 10.10.10.1
614 Now after a final check whether all changed information is correct we save it
615 and see again the <<edit-corosync-conf,edit corosync.conf file>> section to
616 learn how to bring it in effect.
618 As our change cannot be enforced live from corosync we have to do an restart.
620 On a single node execute:
623 systemctl restart corosync
626 Now check if everything is fine:
630 systemctl status corosync
633 If corosync runs again correct restart corosync also on all other nodes.
634 They will then join the cluster membership one by one on the new network.
636 Redundant Ring Protocol
637 ~~~~~~~~~~~~~~~~~~~~~~~
638 To avoid a single point of failure you should implement counter measurements.
639 This can be on the hardware and operating system level through network bonding.
641 Corosync itself offers also a possibility to add redundancy through the so
642 called 'Redundant Ring Protocol'. This protocol allows running a second totem
643 ring on another network, this network should be physically separated from the
644 other rings network to actually increase availability.
646 RRP On Cluster Creation
647 ~~~~~~~~~~~~~~~~~~~~~~~
649 The 'pvecm create' command provides the additional parameters 'bindnetX_addr',
650 'ringX_addr' and 'rrp_mode', can be used for RRP configuration.
652 NOTE: See the <<corosync-conf-glossary,glossary>> if you do not know what each parameter means.
654 So if you have two networks, one on the 10.10.10.1/24 and the other on the
655 10.10.20.1/24 subnet you would execute:
659 pvecm create CLUSTERNAME -bindnet0_addr 10.10.10.1 -ring0_addr 10.10.10.1 \
660 -bindnet1_addr 10.10.20.1 -ring1_addr 10.10.20.1
663 RRP On A Created Cluster
664 ~~~~~~~~~~~~~~~~~~~~~~~~
666 When enabling an already running cluster to use RRP you will take similar steps
668 <<separate-cluster-net-after-creation,separating the cluster network>>. You
669 just do it on another ring.
671 First add a new `interface` subsection in the `totem` section, set its
672 `ringnumber` property to `1`. Set the interfaces `bindnetaddr` property to an
673 address of the subnet you have configured for your new ring.
674 Further set the `rrp_mode` to `passive`, this is the only stable mode.
676 Then add to each node entry in the `nodelist` section its new `ring1_addr`
677 property with the nodes additional ring address.
679 So if you have two networks, one on the 10.10.10.1/24 and the other on the
680 10.10.20.1/24 subnet, the final configuration file should look like:
691 bindnetaddr: 10.10.10.1
695 bindnetaddr: 10.10.20.1
705 ring0_addr: 10.10.10.1
706 ring1_addr: 10.10.20.1
713 ring0_addr: 10.10.10.2
714 ring1_addr: 10.10.20.2
717 [...] # other cluster nodes here
720 [...] # other remaining config sections here
724 Bring it in effect like described in the
725 <<edit-corosync-conf,edit the corosync.conf file>> section.
727 This is a change which cannot take live in effect and needs at least a restart
728 of corosync. Recommended is a restart of the whole cluster.
730 If you cannot reboot the whole cluster ensure no High Availability services are
731 configured and the stop the corosync service on all nodes. After corosync is
732 stopped on all nodes start it one after the other again.
734 Corosync Configuration
735 ----------------------
737 The `/ect/pve/corosync.conf` file plays a central role in {pve} cluster. It
738 controls the cluster member ship and its network.
739 For reading more about it check the corosync.conf man page:
745 For node membership you should always use the `pvecm` tool provided by {pve}.
746 You may have to edit the configuration file manually for other changes.
747 Here are a few best practice tips for doing this.
749 [[edit-corosync-conf]]
753 Editing the corosync.conf file can be not always straight forward. There are
754 two on each cluster, one in `/etc/pve/corosync.conf` and the other in
755 `/etc/corosync/corosync.conf`. Editing the one in our cluster file system will
756 propagate the changes to the local one, but not vice versa.
758 The configuration will get updated automatically as soon as the file changes.
759 This means changes which can be integrated in a running corosync will take
760 instantly effect. So you should always make a copy and edit that instead, to
761 avoid triggering some unwanted changes by an in between safe.
765 cp /etc/pve/corosync.conf /etc/pve/corosync.conf.new
768 Then open the Config file with your favorite editor, `nano` and `vim.tiny` are
769 preinstalled on {pve} for example.
771 NOTE: Always increment the 'config_version' number on configuration changes,
772 omitting this can lead to problems.
774 After making the necessary changes create another copy of the current working
775 configuration file. This serves as a backup if the new configuration fails to
776 apply or makes problems in other ways.
780 cp /etc/pve/corosync.conf /etc/pve/corosync.conf.bak
783 Then move the new configuration file over the old one:
786 mv /etc/pve/corosync.conf.new /etc/pve/corosync.conf
789 You may check with the commands
792 systemctl status corosync
793 journalctl -b -u corosync
796 If the change could applied automatically. If not you may have to restart the
797 corosync service via:
800 systemctl restart corosync
803 On errors check the troubleshooting section below.
808 Issue: 'quorum.expected_votes must be configured'
809 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
811 When corosync starts to fail and you get the following message in the system log:
815 corosync[1647]: [QUORUM] Quorum provider: corosync_votequorum failed to initialize.
816 corosync[1647]: [SERV ] Service engine 'corosync_quorum' failed to load for reason
817 'configuration error: nodelist or quorum.expected_votes must be configured!'
821 It means that the hostname you set for corosync 'ringX_addr' in the
822 configuration could not be resolved.
825 Write Configuration When Not Quorate
826 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
828 If you need to change '/etc/pve/corosync.conf' on an node with no quorum, and you
829 know what you do, use:
835 This sets the expected vote count to 1 and makes the cluster quorate. You can
836 now fix your configuration, or revert it back to the last working backup.
838 This is not enough if corosync cannot start anymore. Here its best to edit the
839 local copy of the corosync configuration in '/etc/corosync/corosync.conf' so
840 that corosync can start again. Ensure that on all nodes this configuration has
841 the same content to avoid split brains. If you are not sure what went wrong
842 it's best to ask the Proxmox Community to help you.
845 [[corosync-conf-glossary]]
846 Corosync Configuration Glossary
847 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
850 This names the different ring addresses for the corosync totem rings used for
851 the cluster communication.
854 Defines to which interface the ring should bind to. It may be any address of
855 the subnet configured on the interface we want to use. In general its the
856 recommended to just use an address a node uses on this interface.
859 Specifies the mode of the redundant ring protocol and may be passive, active or
860 none. Note that use of active is highly experimental and not official
861 supported. Passive is the preferred mode, it may double the cluster
862 communication throughput and increases availability.
868 It is obvious that a cluster is not quorate when all nodes are
869 offline. This is a common case after a power failure.
871 NOTE: It is always a good idea to use an uninterruptible power supply
872 (``UPS'', also called ``battery backup'') to avoid this state, especially if
875 On node startup, service `pve-manager` is started and waits for
876 quorum. Once quorate, it starts all guests which have the `onboot`
879 When you turn on nodes, or when power comes back after power failure,
880 it is likely that some nodes boots faster than others. Please keep in
881 mind that guest startup is delayed until you reach quorum.
887 Migrating virtual guests to other nodes is a useful feature in a
888 cluster. There are settings to control the behavior of such
889 migrations. This can be done via the configuration file
890 `datacenter.cfg` or for a specific migration via API or command line
897 The migration type defines if the migration data should be sent over a
898 encrypted (`secure`) channel or an unencrypted (`insecure`) one.
899 Setting the migration type to insecure means that the RAM content of a
900 virtual guest gets also transfered unencrypted, which can lead to
901 information disclosure of critical data from inside the guest (for
902 example passwords or encryption keys).
904 Therefore, we strongly recommend using the secure channel if you do
905 not have full control over the network and can not guarantee that no
906 one is eavesdropping to it.
908 NOTE: Storage migration does not follow this setting. Currently, it
909 always sends the storage content over a secure channel.
911 Encryption requires a lot of computing power, so this setting is often
912 changed to "unsafe" to achieve better performance. The impact on
913 modern systems is lower because they implement AES encryption in
914 hardware. The performance impact is particularly evident in fast
915 networks where you can transfer 10 Gbps or more.
921 By default, {pve} uses the network in which cluster communication
922 takes place to send the migration traffic. This is not optimal because
923 sensitive cluster traffic can be disrupted and this network may not
924 have the best bandwidth available on the node.
926 Setting the migration network parameter allows the use of a dedicated
927 network for the entire migration traffic. In addition to the memory,
928 this also affects the storage traffic for offline migrations.
930 The migration network is set as a network in the CIDR notation. This
931 has the advantage that you do not have to set individual IP addresses
932 for each node. {pve} can determine the real address on the
933 destination node from the network specified in the CIDR form. To
934 enable this, the network must be specified so that each node has one,
935 but only one IP in the respective network.
941 We assume that we have a three-node setup with three separate
942 networks. One for public communication with the Internet, one for
943 cluster communication and a very fast one, which we want to use as a
944 dedicated network for migration.
946 A network configuration for such a setup might look as follows:
949 iface eth0 inet manual
953 iface vmbr0 inet static
955 netmask 255.255.250.0
963 iface eth1 inet static
965 netmask 255.255.255.0
969 iface eth2 inet static
971 netmask 255.255.255.0
974 Here, we will use the network 10.1.2.0/24 as a migration network. For
975 a single migration, you can do this using the `migration_network`
976 parameter of the command line tool:
979 # qm migrate 106 tre --online --migration_network 10.1.2.0/24
982 To configure this as the default network for all migrations in the
983 cluster, set the `migration` property of the `/etc/pve/datacenter.cfg`
987 # use dedicated migration network
988 migration: secure,network=10.1.2.0/24
991 NOTE: The migration type must always be set when the migration network
992 gets set in `/etc/pve/datacenter.cfg`.
996 include::pve-copyright.adoc[]