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Re: [Linux-cluster] cmirror and RHEL 5



Nikolas Lam napisaƂ(a):
> On Mon, 2007-10-22 at 16:39 +0300, Mikko Partio wrote:
>> Hello list
>>
>> does RHEL 5 support cmirror (creating lvm mirrored volumes in a
>> cluster environment)? I can't find any rpm packages for it. My goal is
>> to increase redundancy by mirroring data between two sans. 
>>
>> Regards
>>
>> M
> 
> Hi Mikko,
> 
> Unfortunately the answer is no at the moment. This and LVM snapshots are
> two things that I know can't be done with RHEL5's CLVM yet. I've been
> told by Red Hat consultants that update 2 is the current target for
> these features.
> 
> We wanted to use this solution to automate SAN failover between two HP
> EVAs in different data centres but in the end have ended up having to
> use HP's Continuous Access system to handle mirroring behind the scenes.
> Fortunately we were already needed this mirroring elsewhere in the
> university because I'm told the license costs six figures, which is a
> lot more expensive than host based mirroring (0 dollars ;).
> 
> In some ways this is better because it removes a potential split brain
> scenario that could happen if host-based mirroring was used. But it does
> require manual intervention by a SAN administrator in the event of EVA
> failure, which is not going to happen quickly if it happens, say at 3am.

You can use LVM on the top of DRBD [1]. It is very simple to implement
with bash scripts(manual failover) or with Heartbeat(automatic failover)
[2]. In my opinion DRBD is better solution than cmirror, because you
don't need third device.

[1] - http://www.drbd.org/
[2] - http://www.linux-ha.org/

Best Regards
Maciej Bogucki


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