Redundant/failover NFS servers - stale NFS file handle

[Attila Nagy]

On 2006. 08. 14. 17:55, Oliver Fromme wrote:
> We use NetApp Filer clusters (NAS) for that purpose.
> They aren't cheap, but they work very well.
I don't like blackboxes with nice GUIs. :)

> NFS file handles are based on the inode number.  That means
> if you want to have a fail-over that's transparent for the
> client, your NFS servers would need to have the same inode
> numebrs for their files.  Normally, the only way to achieve
> that is to duplicate the file system from the master to the
> slaves using dd(1).
I've already did that (a vnode backed md), but that's not too 
comfortable in the long run.

> There's another possibility, but I haven't tried it for
> myself, so it's just theory.  :-)   You can try to put
> geom_mirror (see gmirror(8)) on top of geom_gate (see
> ggated(8), ggatec(8)).  Then you will have a RAID1 with
> one component local and the other component remote.
> However, I think it only works reliably in read-only
> mode.
Yes, both of them must be read only, several years ago I've used a 
similar setup, but with a shared SCSI disk.
Read only on the client side is OK for me, but is hard to maintain on 
the server side.
I guess it would be possible to do this RW, mounted only on the master 
and if it fails, remounted (fscked, etc) on the slave, but I consider 
that a little bit hackish. I can solve this problem with Linux, but I 
would like to do it with FreeBSD, that's why I'm asking. Maybe somebody 
has a clever idea, which can make it possible on FreeBSD, without the 
above hassles.
Of course what is really needed here is a cluster filesystem, or an NFS 
server/file system which can solve this problem at its level.

> I don't know if this is an option for you, but you can
> also put a minimal root file system into the kernel
> (md file system), just sufficient to get networking +
> AMD running, and mount everything else via NFS.  Another
Yes, I've also thought of that, but that has drawbacks too.

Thanks for the ideas.
-- 
Attila Nagy                                   e-mail: Attila.Nagy at fsn.hu
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