[Linux-HA] Cluster aware LVM.

[Andrew Beekhof]

On Dec 17, 2007, at 8:58 PM, Alain St-Denis wrote:

> Hi,
>
> I managed to configure Redhat's cman in order to use clvmd within our
> heartbeat2 clusters which are attached to a shared SAN. While  
> working on
> this, I felt it was a bit redundant to use 2 cluster managers (cman  
> and crm)
> in the same cluster. Has there been any work done to have clvmd  
> adapted to
> crm? Would that be a lot of work?

Now that the crm can run on openAIS (which i believe is what cman  
uses), the crm and clvmd can use the same membership information....  
so in theory it should be possible.
I don't know much about clvmd, but if you write an RA for it, then it  
may "just work".

It certainly sounds like something worth pursuing.

> I am considering using clvmd to gard our non-shared file systems  
> living on a
> shared SAN against accidental concurrent access. In order to achieve  
> this, I
> would have to modify the LVM RA to have it work at the logical  
> volume level
> instead of the volume group level. The idea would be to use  
> exclusive locks
> to guarantee only one node accesses a logical volume resource. This  
> would
> require that our volume groups be made cluster aware. This CLVM RA  
> would
> run "lvchange -a ey /some_lv" when starting a resource and would  
> fail if the
> lock can't be acquired.
>
> I'd like your opinion: am I on the right track? Given properly  
> configured
> stonith resources, I haven't made up my mind if this is useful at  
> all... It
> (this CLVM RA) might be a good protection against human mistake  
> since trying
> to access a lv from another node would fail. A sysadmin could still  
> activate
> the lv since the lock is advisory, but it should give someone a hint.
>
> If other methods to achieve the same goal already exist, please  
> describe them
> or show me where I can find any relevant docs.
>
> Thanks and regards,
>
> Alain
>
> -- 
> Alain St-Denis
> Supercomputing, Systems and Storage
> Canadian Meteorological Centre
> Meteorological Service of Canada
> Environment Canada
> Tel: +1 514 421 4697
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