[Pacemaker] DRBD and fencing

[Martin Aspeli]

Martin Aspeli wrote:
> Hi folks,
>
> Let's say have a two-node cluster with DRBD and OCFS2, with a database
> server that's supposed to be active on one node at a time, using the
> OCFS2 partition for its data store.
>
> If we detect a failure on the active node and fail the database over to
> the other node, we need to fence off the shared storage in case the
> active node is still writing to it.
>
> Can this be done in such a way that the local DRBD/OCFS2 refuses to
> accept writes from the now-presumed-dead node? I guess this would be
> similar to putting an access rule on a SAN to block off the previously
> active node from attempting to read or write any data.
>
> Is this feasible?

We went off on a side-track, I think, but I'd still like to know the 
answer: Can one "fence" at the DRBD level?

 From the thread, it sounds like we'll not use OCFS2 for the Postgres 
data store, but would still use DRBD, e.g. with ext4 or whatever. The 
fencing problem would then be equally, if not more, acute.

It's basically between doing something at the DRBD level, if that's 
feasible, or using the DRAC IPMI device on our server to shoot it.

Martin