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Date: Tue, 21 Oct 2003 20:08:53 -0400
To: "Robert J. Adams (jason)" <radams@siscom.net>
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From: Nathan Hawkins <utsl@quic.net>
cc: freebsd-fs@freebsd.org
Subject: Re: >1 systems 1 FS
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On Tue, Oct 21, 2003 at 07:53:23PM -0400, Robert J. Adams (jason) wrote:
> Alfred Perlstein wrote:
> 
> >>Hello,
> >>
> >>I'm working on a new cluster design and had a quick question. If I have 
> >>a few boxes mounting the same FS (over a SAN) all read-only will it 
> >>work? Will I have any trouble? Has anyone tried this with UFS/UFS2 ..
> >
> >
> >You shouldn't.
> 
> I shouldn't do this or I shouldn't have trouble? :)

No, you can get away with _all_ read only. It's the part where you mount
RW somewhere that causes trouble. There is a little problem of cache
coherency.

> >>Lets take it one step further.. lets say I have 1 box that mounts it 
> >>RW.. and it updates the contents .. will the other systems that have it 
> >>mounted RO puke?
> >
> >
> >Likely.
> 
> Well shit.. I need this.

There are some options:
1. Go to NAS, and use NFS.
2. Switch OS to one that has a cluster filesystem
3. Implement a filesystem with cluster support
4. Don't use a filesystem, use devices, and work around the problem in
userspace