* The root password of a cluster node is required for adding nodes.
+* Online migration of virtual machines is only supported when nodes have CPUs
+ from the same vendor. It might work otherwise, but this is never guaranteed.
+
NOTE: It is not possible to mix {pve} 3.x and earlier with {pve} 4.X cluster
nodes.
[[pvecm_cluster_network_requirements]]
Network Requirements
~~~~~~~~~~~~~~~~~~~~
-This needs a reliable network with latencies under 2 milliseconds (LAN
-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).
+
+The {pve} cluster stack requires a reliable network with latencies under 5
+milliseconds (LAN performance) between all nodes to operate stably. While on
+setups with a small node count a network with higher latencies _may_ work, this
+is not guaranteed and gets rather unlikely with more than three nodes and
+latencies above around 10 ms.
+
+The network should not be used heavily by other members, as while corosync does
+not uses much bandwidth it is sensitive to latency jitters; ideally corosync
+runs on its own physically separated network. Especially 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. To ensure that the nodes can connect to each other on the
for Debian based hosts, and 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 cluster's LAN and can have longer
-latencies than 2 ms.
+NOTE: Unlike corosync itself, a QDevice connects to the cluster over TCP/IP.
+The daemon can also run outside the LAN of the cluster and isn't limited to the
+low latencies requirements of corosync.
Supported Setups
~~~~~~~~~~~~~~~~
NOTE: Make sure that the SSH configuration on your external server allows root
login via password, if you are asked for a password during this step.
+If you receive an error such as 'Host key verification failed.' at this
+stage, running `pvecm updatecerts` could fix the issue.
After you enter the password and all the steps have successfully completed, you
will see "Done". You can verify that the QDevice has been set up with:
mind that guest startup is delayed until you reach quorum.
+[[pvecm_next_id_range]]
+Guest VMID Auto-Selection
+------------------------
+
+When creating new guests the web interface will ask the backend for a free VMID
+automatically. The default range for searching is `100` to `1000000` (lower
+than the maximal allowed VMID enforced by the schema).
+
+Sometimes admins either want to allocate new VMIDs in a separate range, for
+example to easily separate temporary VMs with ones that choose a VMID manually.
+Other times its just desired to provided a stable length VMID, for which
+setting the lower boundary to, for example, `100000` gives much more room for.
+
+To accommodate this use case one can set either lower, upper or both boundaries
+via the `datacenter.cfg` configuration file, which can be edited in the web
+interface under 'Datacenter' -> 'Options'.
+
+NOTE: The range is only used for the next-id API call, so it isn't a hard
+limit.
+
Guest Migration
---------------
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
+Setting the migration type to `insecure` means that the RAM content of a
virtual guest is also transferred unencrypted, which can lead to
information disclosure of critical data from inside the guest (for
example, passwords or encryption keys).
always sends the storage content over a secure channel.
Encryption requires a lot of computing power, so this setting is often
-changed to "unsafe" to achieve better performance. The impact on
+changed to `insecure` to achieve better performance. The impact on
modern systems is lower because they implement AES encryption in
hardware. The performance impact is particularly evident in fast
networks, where you can transfer 10 Gbps or more.
projects / pve-docs.git / blobdiff