[OpenAFS] Resilience

[Douglas E. Engert]

Wheeler, JF (Jonathan) wrote:
> One of our (3) AFS servers has a mounted read-write volume which must be
> available 24x7 to our batch system.  The server is as resilient is we
> can make it, but still it may fail outside normal working hours for some
> reason.  For technical reasons related to the software installed on the
> volume it is not possible to use read-only volumes mounted from our
> other servers (the software must be installed and served from the same
> directory name), so I have devised the following plan in the event of a
> failure: 

The way I read the above, is that only during install do you need write
access to the sofware. After the install, do you still need write access
to all or part of the software? If so can you put the write part
on its own RW volume, but keep the rest replicated? Symlinks for selected
files to the files in tghe RW volume could be used.

With many open source packages, you can use --prefix, DESTDIR= and -rpath
to force the install to be into /afs/.site/...  but look in /afs/site/...

Or on the first install, don't have any read only volumes,
then the install is done to /afs/site/... After install, then
replicate...

It does not sound like this software changes very often.

> 
> a) create read-only volumes on the other 2 servers, but do not mount
> them; use "vos release" whenever the software is updated
> b) in the event of a failure of server1 (which has the rw volume), drop
> the existing mount and mount one of the read-only volumes (we can live
> with the read-only copy whilst server1 is being repaired/replaced) in
> its place.

If you can live with RO while it is being repaired, why can't you
live with it with longer? That sounds like there is no requirement for
RW.

> 
> Can anyone see problems with that scenario ?  We could use "vos
> convertROtoRW"; how would that affect the process ?
> 
> Jonathan Wheeler 
> e-Science Centre 
> Rutherford Appleton Laboratory
> 
> 

-- 

  Douglas E. Engert  <DEEngert@anl.gov>
  Argonne National Laboratory
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  Argonne, Illinois  60439
  (630) 252-5444