[linux-lvm] LVM snapshot with Clustered VG

[Vladislav Bogdanov]

06.03.2013 15:17, Andreas Pflug wrote:
> Am 06.03.13 12:20, schrieb Vladislav Bogdanov:
>>>> I'm running corosync 1.4.2 (debian wheezy).
>>>> Which cluster manager interface does clvmd detect? corosync or openais?
>>>> You should use former, openais one is(was) using LCK service which is
>>>> very unstable.
>>> It's using openais. I'm not too happy about the stability, so maybe I'd
>>> switch to corosync now.
>> That could be the problem btw. I did neither test nor look at openais
>> module implementation in clvmd, because I had plenty problems with it
>> (actually with LCK under it) in the past, so I even forced to use
>> corosync (CPG) + dlm instead of detected openais (CPG+LCK) for older
>> systems (look at -I switch of clvmd).
>>
>> And, openais is deprecated upstream, so I do not see any reason to use
>> it. Even gfs_controld (which is probably the only well-known user of
>> openais services) actually does not strictly require it, at least I was
>> able to port it to pure CPG+DLM with dlm4 on top of corosync2, which is
>> not compatible with openais plugins.
>>
>> Also you may need quorum patch found in this list, it does its job well.
>>
>>> Could this be a reason for the x-lock failure as well?
> You just answered the quirky question :-)
> 
> Unfortunately, corosync/dlm don't work for me as expected. When starting
> clvmd -I corosync (with dlm kernel module loaded), creating the dlm
> lockspace "clvmd" fails, with
> 
> dlm: no local IP address has been set
> dlm: cannot start dlm lowcomms -107
> 

You need to have dlm_controld running on all nodes.
And that is not trivial with corosync1. You need to either use cman or
use deprecated dlm_controld.pcmk which was removed from a cluster (cman)
package after 3.0.17. Latter does not work well without heavy patching
(http://www.mail-archive.com/pacemaker@oss.clusterlabs.org/msg09959.html
,
http://www.mail-archive.com/pacemaker@oss.clusterlabs.org/msg11123.html
and
http://oss.clusterlabs.org/pipermail/pacemaker/2012-February/013073.html).
Even after that there are some problems with it.

Latest versions (4.x) of dlm (it was split from cman) work fine with
corosync2 and pacemaker 1.1.6+. But I doubt it can ever be compiled with
corosync1. Yes, it cannot, because it requires quorum which appeared in
corosync2.

You may look at thread
http://oss.clusterlabs.org/pipermail/pacemaker/2012-October/015826.html
for some info.

That's all why I moved to corosync2. You can search through pacemaker
list archives for dlm-related messages from me to get full picture.

You may also look at slides I presented at LVEE winter 2013:
http://lvee.org/uploads/image_upload/file/267/Linux_Clusters_at_LVEE_2013.pdf


> I haven't found any hint what might go wrong on the machine (checked
> already hostname resolves correctly to its ip address via /etc/hosts;
> corosync uses that network too).
> 
> Regards
> Andreas