NFS server fail-over - how do you do it?

[adp]

Very useful information, thanks. We have a very stable NFS server, but I am
still working hard to put some redundancy into place. I was thinking that
since NFS is udp-based, that if the primary NFS server failed, and the
secondary assumed the primary NFS server's IP address, that things would at
least return to normal (of course, any writes that had been in progress
would fail horribly). That doesn't seem to be the case. During a test we
killed the main NFS server and brought up the NFS IP as an alias on the
backup. Didn't work. Has anyone tried anything like this?

----- Original Message -----
From: "Chuck Swiger" <cswiger at mac.com>
To: "adp" <dap99 at i-55.com>
Cc: <questions at freebsd.org>
Sent: Monday, May 31, 2004 11:55 AM
Subject: Re: NFS server fail-over - how do you do it?


> adp wrote:
> > One of my big problems right now is that if our primary NFS server goes
down
> > then everything using that NFS mount locks up. If I change to the
mounted
> > filesystem on the client then it stalls:
> >
> > # pwd
> > /root
> > # cd /nfs-mount-dir
> > [locks]
> >
> > If I try to reboot the reboot fails as well since FreeBSD can't unmount
the
> > filesystem!?
>
> Solaris provides mechanisms for NFS-failover for read-only NFS shares, but
> FreeBSD doesn't seem to support that.  Besides, most people seem to want
to
> use read/write filesystems, which makes the former solution not very
useful to
> most people's requirements.
>
> The solution to the problem is to make very certain that your primary NFS
> server does not go down, ever, period.  Reasonable people who identify a
> mission-critical system such as a primary NFS server ought to be willing
to
> spend money to get really good hardware, have a UPS, and so forth to
facility
> the goal of 100% uptime.  A Sun E450 still makes a nice primary
fileserver,
> although NAS solutions like a NetApp or an Auspex (not cheap!) should also
be
> considered.
>
> The other choice would be to switch from using NFS to using a distributed
> filesystem which implements fileserver redundancy, such as AFS and it's
> successor, DFS.
>
> --
> -Chuck
>
>