[Linux-cluster] GFS + DRBD Problems

[Lon Hohberger]

On Mon, 2008-03-03 at 16:22 +0000, gordan at bobich.net wrote:
> On Mon, 3 Mar 2008, Lon Hohberger wrote:
> 
> >> I have a 2-node cluster with Open Shared Root on GFS on DRBD.
> >
> > Last week, I saw a car with a license plate from 'Wyoming'.  Now,
> > someone's running GFS on shared root DRBD.  My world's turning upside
> > down.
> 
> LOL! We live in interesting times. :)
> And anyway, what's wrong with GFS shared root on DRBD? :)

(Note: That was not a stab at Wyoming or its residents; it was a joke
referencing the Wyoming Conspiracy Theory which asserts that Wyoming
does not exist.)


> I can't see any evidence of that, and I'd expect to see something on the 
> console about it, too. I'll set up a remote syslog to double-check.

CMAN doesn't log to the console for this sort of thing, it goes to
syslog... but of course, if root's on GFS and access to that GFS is
blocked, it might be missed in /var/log/messages.


> > Off the top of my head, this sounds like a DRBD thing.  If sync's
> > completed, it works, right?
> 
> Not quite - it works in as far as it gets as far as mounting the file 
> system without noticing it to be inconsistent (presumably because it isn't 
> changing underneath it). But the FS gets corrupted.
> 
> I cannot be sure right now, but I have a suspicion that both machines 
> might be trying to mount the FS with the same journal. I could be 
> mis-remembering and/or mis-interpreting what mount output says when it's 
> connecting, though. I'll check it via the remote console in a bit and 
> paste the output from each node.

Well, after fencing completes, one node replays the other node's
journal, but then it stops using it AFAIK.  When the other node boots,
it uses its own journal (or should be).

-- Lon