Veritas-bu

[Veritas-bu] Does SSO Use SCSI Reserve/Release?

2001-05-31 12:55:36
Subject: [Veritas-bu] Does SSO Use SCSI Reserve/Release?
From: curtis AT backupcentral DOT com (W. Curtis Preston)
Date: Thu, 31 May 2001 09:55:36 -0700
I'm getting conflicting information from a couple of different sources, and 
I KNOW that someone out there knows the real answer.

How does SSO (for NetBackup & BE if possible) managed contention for the 
robot? It would seem that this could be done in one of two ways:

1. It uses the SCSI Reserve command when it starts to use the arm.
    If no other host is using it, the command will work, and it will proceed.
    If another host is using it, the command will fail, and it will have to 
be retried.

2. It doesn't need to use the SCSI Reserve command, because it is accepting 
all the requests.
    Requests for the robot are "queued," and each host needing the robot is 
told to wait it's turn.
    SCSI Reserve is not needed, because the software will insure that only 
one robotic command is issued at a time.

3. Same as #2, except it also uses SCSI Reserve.  It doesn't NEED to, but 
it does anyway.
    Why?  I don't know. ;)

It would SEEM that #2 would be preferable.



---
W. Curtis Preston
Principal Consultant for Storage Designs, your storage experts
Webmaster: http://www.backupcentral.com Phone: 760 631 7991


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