[Lustre-discuss] Failover Setup MDS/MDT

[Heiko Schroeter]

Am Freitag, 20. Juni 2008 16:20:23 schrieb Bernd Schubert:
> On Friday 20 June 2008 16:08:23 Brian J. Murrell wrote:
> > On Fri, 2008-06-20 at 16:01 +0200, Bernd Schubert wrote:
> > > We do it for several lustre installations and it works fine.
> >
> > Have you done any "intensive" failover testing of it?  I'm thinking
> > something along the lines of our Hendrix/CMD test 11 or 17.  In those
> > tests we had to survive a constant stream of failovers at something like
> > 3 or 5 minute intervals for 24 hours.  So yes, a hundred or two
> > failovers in a row and no application (i.e. userspace) errors.
>
> I don't think we did these tests yet, but I could put it onto my TODO list,
> if you think it is important. So far drbd always perfectly did its job and
> never was an issue here (in contrary of the many many hardware problems we
> often have).

The failover takes about 3-4 minutes in our setup with an shared MDS and MDT 
running a mirrored DRBD device.
As far as we can see it this is taken by the fsck on the DRBD device when 
HEARBEAT takes over.
The MDS/MDT partition used in this test szenario is 20GB in size running in a 
1.8GHz AMD machine.


Just one more question about the partition sizes. As the docs points out one 
determines the size for the MDS partition by the number of inodes.

How can one determine the size for the MDT partition or is that the same as 
the MDS device ?
(As far as i can see the MDT takes the DIR info etc. So it should be larger 
than the MDS.)

Thanks
Heiko