[DRBD-user] Difference between Inconsistent and Uninitialised

[En Chiang Lee]

Hi,

How does one tell the difference between uninitialised meta-disk and
inconsistent data?

Here's the context:

I'm trying to setup root filesystem failover on an OpenSSI cluster by
mirroring the root with DRBD. The version of DRBD is 0.7.5, modified to
use the cluster heartbeat (CLMS) to change 'primary-ship' in case of
node failure.

drbdadm does not allow me to attach to a mounted device. So, for root, I
tried putting the following calls in the initrd:
  drbdadm up r0
  drbdadm primary r0
where r0 is the resource name. Of course, 'drbdadm primary r0' fails,
saying that I should use '--do-what-I-say', since the "Local replica is
inconsistent".

So, I replaced that with
  drbdadm -- --do-what-I-say -- primary r0
which succeeds, and I have an OpenSSI cluster which is capable of
failover.

Now the problem is that, with "--do-what-I-say" in the initrd, the first
of the two nodes to boot in the cluster would always mark itself as
consistent since it cannot tell whether the drbd device is inconsistent
or uninitialised.

What I'm looking for is a way to allow the node to wait for it's
consistent partner in the case of inconsistency, and to go ahead and
mark itself as consistent in the case of uninitialised metadata.

Thanks in advance,

En Chiang