Date: Tue, 7 May 2002 18:21:08 +0200
From: =?iso-8859-1?Q?Ragnar_Kj=F8rstad?= <xfs@ragnark.vestdata.no>
To: Stephen Lord <lord@sgi.com>
Cc: Hugo Lafargue <admin@greu.net>, linux-xfs@oss.sgi.com
Subject: Re: Exporting xfs over nfs
Message-ID: <20020507182108.S18743@vestdata.no>
References: <20020507154732.HHEI7485.mtiwmhc26.worldnet.att.net@taz> <3CD7FAF2.5040601@sgi.com>
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In-Reply-To: <3CD7FAF2.5040601@sgi.com>; from lord@sgi.com on Tue, May 07, 2002 at 11:04:02AM -0500
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On Tue, May 07, 2002 at 11:04:02AM -0500, Stephen Lord wrote:
> First of all, I presume when you fail over to the second node, you 
> unmount the xfs filesystem on one
> box and mount it on the second one before the IP address takeover 
> happens? If not then there is
> a good chance of corruption.

Yes, that's the way it's done. Most cluster-implementations also
implement some kind of fencing to make sure the original server doesn't
continue accessing the disk after the second server takes over.

> That aside, I think that without code changes, the only way to make this 
> work is to ensure that the
> /dev entry used to mount the filesystem on both boxes has the same 
> major/minor number. If not
> then I think the stale handles will result. Note this is just a guess on 
> my part right now, I have
> not looked at this code in a while.

Recently a patch was accepted to allow the user to specify the device-id
to use for nfs exports - that should take care of the problem with
different major/minor numbers on the two servers. But of course, having
to identical servers are the easiest way.


You also need to put /var/lib/nfs on shared storage, and to use the same
"servicename" on both servers (-n flag in newest version of nfs-utils)
for locks to work properly.

There are other cavecats as well, but basicly it's possible to get it to
work with a little effort. 

And for out-of-the-box solutions there are ofcourse NAS devices that you
can buy that implement this :-)


-- 
Ragnar Kjørstad
Big Storage