[Samba] ctdb and AllowMixedVersion

Martin Schwenke martin at meltin.net
Thu Sep 16 23:01:55 UTC 2021

Hi Uli,

On Wed, 15 Sep 2021 10:04:07 +0000, "Sibiller, Ulrich via samba"
<samba at lists.samba.org> wrote:

> we are using ctdb to export a Spectrum Scale filesystem via nfsv3
> (kernel nfs, not ganesha, not Spectrum Scale CES). We have four nodes
> that are members of the ctdb, serving 8 IPs in two networks (4 in
> each). The systems have been setup with RHEL8.3, using the provided
> ctbd 4.12. Updating those systems to RHEL8.4 reveals that Red Hat
> switched ctdb to 4.13 so the ctdb on an updated node ceases to work
> together with the others still having ctdb 4.12.
> ctdb offers AllowMixedVersions to disable the version check but at
> the same time discourages its use:
> https://wiki.samba.org/index.php/Upgrading_a_CTDB_cluster
> As we are NOT using samba on these nodes but only nfsv3 I wonder if
> using AllowMixedVersions might be tolerable in this scenario. 

It is more likely to be tolerable in this scenario, mostly due to this
being NFS-only.   Additionally, I can't see any changes between 4.12 and
4.13 that will cause problems - CTDB development has been quite slow in
the last couple of years.

These days smbd has a version check too, but you will not be subject to

A recent bug fix in Samba >= 4.13 may cause an additional warnings to be
logged during rolling upgrade but these warnings are harmless.

> Besides, in a 2017 discussion on samba-technical plan for a rolling
> update feature are mentioned once the databases "have settled"
> (https://lists.samba.org/archive/samba-technical/2017-May/120760.html).
> So what's the current state of all that?

Hmmm... I don't think that was a real commitment to getting rolling
upgrades working, just recognition that we have a lot of work to do.

Not much restructuring has been done in CTDB since then due to lack of
available development time.  However, I'm optimistic that we can
soon make enough progress to really break rolling upgrades for CTDB in
Samba 4.16! ;-)

peace & happiness,

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