[ClusterLabs] Antw: Re: DLM, cLVM, GFS2 and OCFS2 managed by systemd instead of crm ?

[Ulrich Windl]

>>> Roger Zhou <ZZhou at suse.com> schrieb am 16.10.2019 um 08:54 in Nachricht
<b3e1bcfc-b361-7f76-6b8a-9563c4fd6590 at suse.com>:
> Hi Bernd,
> 
> Apart from Ken's insights.
> 
> I try to put it simple between systemd vs. pacemaker:
> 
> pacemaker does manage dependencies among nodes, well, systemd just not.

What I also wanted to say is (maybe the reason for Bernd's message) that many
examples how to configure OCFS or cLVM are very bad regarding extensibility: If
you follow the instructions for OCFS2, and then you want to follow the
instructions for cLVM (just one example), you get a conflict as DLM already is
configured, and it's not very clear how to resolve dependencies correctly. If
you do it cLVM first, then OCFS2, you have the same problem. Likewise for
clustered RAID.

Regards,
Ulrich

> 
> Cheers,
> Roger
> 
> On 10/16/19 5:16 AM, Ken Gaillot wrote:
>> On Tue, 2019‑10‑15 at 21:35 +0200, Lentes, Bernd wrote:
>>> Hi,
>>>
>>> i'm a big fan of simple solutions (KISS).
>>> Currently i have DLM, cLVM, GFS2 and OCFS2 managed by pacemaker.
>>> They all are fundamental prerequisites for my resources (Virtual
>>> Domains).
>>> To configure them i used clones and groups.
>>> Why not having them managed by systemd to make the cluster setup more
>>> overseeable ?
>>>
>>> Is there a strong reason that pacemaker cares about them ?
>>>
>>> Bernd
>> 
>> Either approach is reasonable. The advantages of keeping them in
>> pacemaker are:
>> 
>> ‑ Service‑aware recurring monitor (if OCF)
>> 
>> ‑ If one of those components fails, pacemaker will know to try to
>> recover everything in the group from that point, and if necessary,
>> fence the node and recover the virtual domain elsewhere (if they're in
>> systemd, pacemaker will only know that the virtual domain has failed,
>> and likely keep trying to restart it fruitlessly)
>> 
>> ‑ Convenience of things like putting a node in standby mode, and
>> checking resource status on all nodes with one command
>> 
>> If you do move them to systemd, be sure to use the resource‑agents‑deps
>> target to ensure they're started before pacemaker and stopped after
>> pacemaker.
>> 
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