Re: [pve-devel] [PATCH docs 1/7] pvecm: drop notes about old version incompatibilities

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 07.05.25 um 17:22 schrieb Kevin Schneider:
> On 29.04.25 15:57, Aaron Lauterer wrote:
>> Signed-off-by: Aaron Lauterer <a.lauterer@proxmox.com>
>> ---
>>   pvecm.adoc | 12 ------------
>>   1 file changed, 12 deletions(-)
>>
>> diff --git a/pvecm.adoc b/pvecm.adoc
>> index 18f7389..47e42e2 100644
>> --- a/pvecm.adoc
>> +++ b/pvecm.adoc
>> @@ -77,18 +77,6 @@ Requirements
>>   * 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.
>> -
>> -NOTE: While it's possible to mix {pve} 4.4 and {pve} 5.0 nodes, doing so is
>> -not supported as a production configuration and should only be done temporarily,
>> -during an upgrade of the whole cluster from one major version to another.
>> -
>> -NOTE: Running a cluster of {pve} 6.x with earlier versions is not possible. The
>> -cluster protocol (corosync) between {pve} 6.x and earlier versions changed
>> -fundamentally. The corosync 3 packages for {pve} 5.4 are only intended for the
>> -upgrade procedure to {pve} 6.0.
>> -
>>   
>>   Preparing Nodes
>>   ---------------
> 
>   In 8.2 we modernized the handling of host keys for SSH connections 
> between cluster by moving them onto the cluster filesystem. We also 
> introduced symlinks for the ceph.client.admin.keyring and ceph.conf 
> files. So =<8.1 and =>8.3 are not compatible.
> 
> For the documentation it would probably the best to either include 
> recent limitations or clearly state, that nodes should only have a 
> single dot release difference between each other  and give examples like:
> 
> Perfect: All Nodes are up to date
> 
> Good: 8.1 and 8.2
> 
> Bad: 8.1 and 8.3 ; 8.1 and 8.2 and 8.3
That's not general true though, the following is:
- we try hard to always allow forward-upgrades.
- in the end all nodes should run the same version.

That means, admins should upgrade all nodes, one after another, and
if the–whyever that is–did not do that they cannot have expect full
compatibility no matter what the version difference is but can expect
that upgrading the older node(s) will work and will make the cluster
fully compatible again.


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