you can't have simultanous SAN and NAS-write access to a LUN.  You can
have SAN + Readonly access to the files.  Or you can have NAS write access
if SAN access is temporarily disabled.

you can do a san backup while the NFS clients are in a read-only state.

how many files are you talking about?  how big are the files?  do you want
to set this up new, or do you have existing files?

what you could do is this:

create LUNs for each file you intend to use this way (lun create).
map them to your backup server (lun map).
offline the luns (lun offline).
make the luns read/writeable from NFS (lun share <lunpath> all)

now do your usual NFS applications, but you have some restrictions.
1) can't delete the file
2) can't resize the file
(there might be more, but those are the big ones)

now when you want to do a backup...

put your NFS applications into a read-only state, or shut them down.

turn off NFS access.  (lun share <lun> none)
online the luns (lun online)

now do your san backup, when you're done, offline the luns, and turn
sharing on.

Another way that would eliminate the file access restricitons would be to
only create the luns when you needed to do the backups.  This could cause
the files to be resized (the files have to align to SCSI disk geometries
etc) but you'd have less restrictions.  You'd stop the NFS app from
writing, create the lun, map the lun, backup the lun, destroy the lun, and
restart the NFS app.

Britt

On Tue, 8 Jul 2003, Kerry Herschel wrote: