We run into this constantly.  We can turn on binding on our QLOGIC card
to make the logical Windows names be consistent with the library WWN,
but it only works if all tapes are found with the Windows SCSI scan.  If
a tape goes offline, it sometimes shifts the logical names around.

We have our tape drives FC to the storage nodes.

-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of Dave Mussulman
Sent: Thursday, September 07, 2006 10:05 AM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: [I] Re: [Networker] NetWorker + Windows SAN Tapes

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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