Subject: Multi-path SCSI
To: None <tech-kern@NetBSD.org>
From: Bill Studenmund <email@example.com>
Date: 09/20/2004 17:20:41
Content-Type: text/plain; charset=us-ascii
With the advent of SANs (Storage Area Networks), a SCSI disk can be
discovered via more than one path. For instance, it's quite reasonable to
have an FC SCSI disk with two connections hooked to two different storage
networks. If a NetBSD box has a FC HBA hooked to each net, it will find
the drive on each net as an independent drive. So for instance sd3 and sd7=
really are the same disk.
SCSI has a way to notice this. The INQUIRY command has a facility called=20
VPD ("Vital Product Details"), which includes a world-unique serial=20
number. So if we find a SCSI disk, we can ask for this VPD page, and see=20
if it matches the serial number of a matching drive.
The question is what do we do if we find a match?
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