I usually term persistent binding in windows as "tending to order
tape drive device links based on scsi bus/device order". With an
emphasis on "tending". In most cases, you'll get OS names that follow
the persistent binding--even more so when you have multiple devices
behind a single scsi id (like with a bridge or VTL), but there is no guarantee.
I midly disagree with Matthew, since the device order isn't
*entirely* arbitrary (scsi id 0 tends to get Tape0, scsi id 1 tends
to get Tape1--if for no other reason than PnP discovers devices in
bus/scsi order), but if you want perfectly reliable, its not.
And if you need to replace a tape drive, and your changer doesn't
forge WWNN and serial number, then it'll find the new device in a
different order, and that order will almost certainly change after a reboot.
There is a very quick cutover to using the windows consistent device
names (which they also term "persistent") or the IBM version of this
for LTO drives. Unless there is a reason you can't use it (version of
NetWorker that is too old to support that feature--I think 7.4.2 was
the first rev), I'd suggest you do.
--Dave
Date: Sat, 27 Jun 2009 12:54:08 -0400
From: Matthew Huff <mhuff AT OX DOT COM>
Subject: Re: Persistent Binding Issue (again)
Because persistent binding means absolutely nothing in Windows in
regards to tapes
Windows has a higher level api called Windows Plug and Play Driver
that assigns device names like //./Tape0. It has nothing to do with
fiber channel or other lower level drivers, so no matter what you do
at the FC or SCSI level, the PnP driver will assign a arbitrary name.
To force those names to be consistent (which is important with tape
drives), you need to set registry settings. Once that is done, the
Plug and Play driver will create names like //./.Tape6455534 based on
your SerialNumber of the tape drive.
===================================
David Gold
Sr. Technical Consultant
Cambridge Computer Services, Inc.
Artists in Data Storage
Tel: 781-250-3000
Tel (Direct): 781-250-3260
Fax: 781-250-3360
dave AT cambridgecomputer DOT com
www.cambridgecomputer.com
===================================
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