[DRBD-user] Mirroring between NFS servers

Bernd Schubert bernd-schubert at gmx.de
Fri Oct 26 19:07:33 CEST 2007

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


On Friday 26 October 2007 18:47:23 Kelsey Cummings wrote:
> On Fri, Oct 26, 2007 at 05:54:38PM +0200, Bernd Schubert wrote:
> > On Friday 26 October 2007 16:51:00 Andreas Haase - evolver group wrote:
> > > On Fri, 26 Oct 2007, Mark Watts wrote:
> > > > DRBD could be used as the backing store for an HA NFS pair, but I
> > > > believe NFS clients would have to reconnect on fail-over since
> > > > file-handle state is stored in memory, not on disk.
> > >
> > > you can replace /var/lib/nfs by a sombolic link to a directory inside
> > > your drbd filesystem. Then switching over to standby node is possible
> > > without remounting filesystems from nfs clients. Depending on used
> > > hardware it could also be necessary to provide as fsid in /etc/exports.
> >
> > In principle not neccessary any more with linux-2.6.x, you need to have
> > mounted /proc/fs/nfsd.
>
> What do you mean by 'in principle' not neccessary anymore with 2.6?  I've
> just finished an active/active NFS cluster with DRBD and heartbeat and had

Active/active with NFS? How are you doing that? Your clients mount from *one* 
IP, but this IP can't be set on both servers at the same time?
Well, one drbd point of view it can be active/active using gfs or ocfs2, but 
from from clients point of view there always can be only one nfs server per 
export.

> trouble with 'stale nfs filehandles' until I moved the nfs state dir to
> something inside the export.

Is /proc/fs/nfsd mounted on your servers? If not, you need to do something 
like "mount -t nfsd nfsd /proc/fs/nfsd", or at it to you fstab.

>
> > The only trouble you still have are these rpc.statd / lockd information
> > in /var/lib/nfs/sm, I think these still should be equal on both servers,
> > but locking information are not part of the NFS protocol (e.g. RFC 1813)
> > up to v3.
>
> No locking here, so that's not a problem for my application.

Even better then :)

Cheers,
Bernd





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