[DRBD-user] DRBD and KVM for a HA-Cluster ?

Digimer linux at alteeve.com
Thu Jan 6 20:02:52 CET 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On 01/06/2011 12:01 PM, Lentes, Bernd wrote:
> Digimer wrote:
> 
>>>>
>>>
>>> I don't want to setup a DRBD as a PV. My idea is to set up 
>> a DRBD on top of a LV, and to format or not format this LV, 
>> depending on the decision to install a KVM into a file or a 
>> plain device.
>>> Is this setup ok ?
>>
>> That would end up being a stacked LVM:
>>
>> <sda1><sdb1>
>>  |
>> <md0>
>>  |
>> <pv>
>>  |
>> <vg>
>>  |
>> <lv(s)>
>>  |
>> <drbd>
>>  |
>> <pv>
>>  |
>> <vg>
>>  |
>> <lv(s)>
>>  |
>> <fs-or-lv/per VM>
>>
>> Is this what you had in mind? Or are you thinking of just 
>> creating raw, standard partitions on the DRBD resource?
>>
>> If it is this, I was doing something similar some time ago, 
>> and it worked. However, after discussing this setup with 
>> Chrissie from RH, she recommended against it when using CLVM 
>> (which I was for a GFS2 partition for shared storage).
>>
>> The reasoning was that it could cause problems as the LVM 
>> would start before the cluster, so the clustered LVM members 
>> would not be available.
>> Unavoidable as I need LVM at node boot-time, long before the 
>> cluster could start. In the end, I decided to forgo LVM on 
>> each node and instead only use LVM on the DRBD.
>>
>> If you are not planning to use LVM on the DRBD resource, but 
>> instead use raw partitions, then you won't use clvm. As for 
>> how well it works, I can't say as I've not tried that. I 
>> can't *think* of any reason why it wouldn't work though.
>>
> 
> I don't want to use a DRBD as a PV.
> 
> My setup is like that:
> 
> <hardware raid>
>  |
> <partition>
>  |
> <PV(s)>
>  |
> <VG>
>  |
> <LV(s)>
>  |
> <DRBD>
>  |
> <FS or vm in a plain LV>
> 
> 
> This should work ?
> Which setup did you discuss with RH ? Your old one or mine ?
> 
> 
> Bernd

I discussed the setup I originally showed. Currently I implement LVM
only on top of DRBD, but I see no reason why DRBD on top of LVM would be
an issue. Of course, LVM can not be clustered in this case, which is
fine. In fact, it's a benefit because, last I checked, snapshot'ing of
clvm was not possible.

-- 
Digimer
E-Mail: digimer at alteeve.com
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