2 NFS server for the same mount point ?

2 NFS server for the same mount point ?

[Maiko Langelaar]

A bit of history first.

Our original NFS server (Server A) is getting old. It exports a
bunch of files systems, ie: /home/u3, /home/u7, under which are
a bunch of user directories.

To minimize downtown, my strategy was to tackle migration to a
new NFS server (Server B) user by user (we don't have tons). In
the end what I have now is all the user directories on Server B,
but I have kept the original mount points still exported on the
Server A, with all the user subdirectories now defined as symbolic
links to the new mount points on Server B. This has worked very
well actually, very little downtime for anyone, and people did
not have to stop computation runs (some of which take weeks).

Now comes the interesting part.

I want to move the original mount points over to Server B !

Question : Can I export the SAME mount points on 2 NFS servers
for the same subnet ? I figure yes, because any particular NFS
client will *target* a particular server. BUT the RPC nature of
the NFS protocol makes me a bit nervous about doing so.

Can anyone provide their experience in this ?

For what it's worth, Server B defaults V4, Server A is V3,
with a mix of V3 and V4 clients.

Much appreciated.

Maiko Langelaar
IT Physics and Astronomy
University of Manitoba
204-474-9273

Re: 2 NFS server for the same mount point ?

[Malahal Naineni]

Maiko Langelaar [maiko@physics.umanitoba.ca] wrote:
> I want to move the original mount points over to Server B !
> 
> Question : Can I export the SAME mount points on 2 NFS servers
> for the same subnet ? I figure yes, because any particular NFS
> client will *target* a particular server. BUT the RPC nature of
> the NFS protocol makes me a bit nervous about doing so.

Yes, you can.

Re: 2 NFS server for the same mount point ?

[Maiko Langelaar]

 > Yes, you can.

Just to be on the safe side, I should be a bit more clear on this.

Both of the NFS servers will be running simultaneously, both
exporting the same mount points for the same subnet.

Maiko

Re: 2 NFS server for the same mount point ?

[J. Bruce Fields]

On Tue, Jul 24, 2012 at 12:05:40PM -0500, Maiko Langelaar wrote:
> > Yes, you can.
> 
> Just to be on the safe side, I should be a bit more clear on this.
> 
> Both of the NFS servers will be running simultaneously, both
> exporting the same mount points for the same subnet.

If you're asking whether it's safe for A and B to both be exporting
something named (for example) "/home"--sure, that's fine.

(If you want the exports from both servers to actually see the same
data, with changes made through A reflected on B and vice versa--at that
point you need a cluster filesystem backing the exports and things
become more complicated.  But I think that's not what you're asking
for.)

--b.