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Subject: Re: Different Ceph versions on OSD/MONs and Clients?
Date: Fri, 5 Jan 2018 15:10:56 +0000
From: Richard Hesketh <richard.hesketh@xxxxxxxxxxxx>
To: Götz Reinicke <goetz.reinicke@xxxxxxxxxxxxxxx>
On 05/01/18 15:03, Götz Reinicke wrote:
> Hi,
>
> our OSD and MONs run on jewel and Centos7. Now I was wondering if an older fileserver with RHEL 6 for which I just found hammer RPMs on the official ceph site can use the RDBs creation on the cluster?
>
> I think there might be problems with some kernel versions/ceph features.
>
> If it is not possible in that combination I have, nevertheless is it possible to run different versions?
>
> Thanks for hints & suggestions . Regards Götz
It is possible for older clients to connect to newer ceph clusters, ceph is generally good about maintaining backwards compatibility on upgrades, with the caveat that if you enable newer features (via the cluster tunables parameters) than the clients can support, they will no longer work (you'll get a version mismatch complaint). Hammer clients on a Jewel cluster should be fine so long as your cluster tunables are at Hammer profile or earlier.
The command "ceph osd crush tunables {PROFILE}" will change your cluster tunables if necessary, but will also result in data movement (as per http://docs.ceph.com/docs/master/rados/operations/crush-map/ ), and may have a performance impact if you have to disable newer features.
Rich
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