[DRBD-user] LVM PV on drbd block device

Juan Antonio pushakk at limbo.ari.es
Fri Nov 13 16:59:27 CET 2009

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


Hi again,

Why the drbd documentation do not reference this issue in the "Configuring
a DRBD resource as a Physical Volume" section?

If I leave the actual configuration like this,

Primary node      -         PV -> /dev/drbd1 -> /dev/md0
Secondary node -         PV -> /dev/md0 (syncronized from /dev/drbd1 on
primary node) with /dev/drbd1 seemingly empty.

What if the primary node is down? I know I can see the LVs data from the
md0 device, and serve the LVs by ISCSI, but will I be able to promote the
secondary node to primary? And could I sync a new node from it in a
permanet failure from the former primary node?

I hope to  have explained correctly.

Thank you very much.
Regards.

> the other

> On Thu, Nov 12, 2009 at 4:49 PM, hans morbus2000 <morbus2000 at web.de>
> wrote:
>
>> [snip]
>>
>> > Hello everyone, the first sorry about my poor english.
>> >
>> > I have configured an drbd8 cluster with two nodes so I have got a
>> > /dev/drbd1 device in both nodes. Later I sync the nodes with "drbdadm
>> --
>> > --overwrite-data-of-peer primary" and the last I did "pvcreate
>> /dev/drbd1"
>> > on primary node.
>> >
>> [snip]
>> on this node
>> # vgchange -a n vgontop
>> # drbdadm secondary drbdx
>>
>> on the other node
>> # drbdadm primary drbdx
>> # vgchange -a y vgontop
>>
>> --> now, lv on top of drbd to be available on both nodes
>>
>> Regards
>> Andreas
>>
>>
>>
> For Juan Antonio:
> which kind of cluster?
> which kind of Linux distribution/release?
> which kind of usage then of the LVs/FS to be created?
>
> For Andreas:
> this is ok for initialization.
> But then you have the same problems when you have to create LVs.
> You need to de-activate VG on one node, demote drbd role, and activate on
> the other... because LVM itslef is not cluster aware.
>
> Preferable, but depending also on the OS kind and licensing, to use drbd
> in
> dual primary mode AND Cluster LVM (with CLVMD that depends on cman and
> cluster-storage channel if using Red Hat, so with economical impact....)
>
> Gianluca
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