On Wed, Sep 06, 2006 at 11:55:38AM +0100, Davina Treiber wrote:
> Gaddy wrote:
> >If, for some reason (defect), we power off a tape drive,
> >some of the Storage Nodes (esp. Windows2003)
> >readdresses the devices "on the fly", e.g. \\.\Tape3 will become \\.\Tape2
> >(SCSI adresses do not change, because they are bound as described above).
> >
> >Unfortunately NetWorker is not very happy with this behavior!
> >( I think, many of you can imagine that, can't you? )
> >
> I don't think there is a way to stop Windows doing this. Even when you 
> have implemented persistent binding there is still no way to force the 
> correct mapping of Windows device files to SCSI addresses. This is a 
> serious design limitation in Windows. Compare this to Solaris where 
> device files are only mapped when you force them to be. I'm not sure how 
> well Linux handles this situation, it is something I have been meaning 
> to find out.

Sorry, I don't have anything to offer on the Windows/SAN front.  But I
know when we transitioned from Solaris to Linux, which (at least by
default) remaps on each reboot, I was annoyed that /dev/nstX could
change depending on what was powered on/connected when the system
booted.  Especially in my test environment where hardware was on and
offline, this was problematic.

I found and have been using scsidev
(http://www.garloff.de/kurt/linux/scsidev/) to map the drives back a
/dev address that relates to their host/channel/id/lun.  scsidev does
this in userspace by looking at what's actually where and creates links
for its real address.  As far as Networker is concerned, I configure it
for /dev/scsi/nsth0-0c0i1l0 and it doesn't care if Linux made it
/dev/nst0 or /dev/nst3.

I'm not sure how that maps to the SAN world, since we're still SAS, but
that's how I do it in Linux.

Dave

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