Good answer.  Actually, both the robot and the drives are shared, but the 
robot is shared more "virtually."  They "share" it by asking one server to 
mount a tape for them.  However, when it comes time to share a drive, they 
do actually communicate directly with the drive.

Perhaps what I am asking is whether or not NetBackup uses SCSI 
Reserve/Release command to reserve the DRIVES, or if it just keeps track of 
who's using what drive when, and doesn't let two servers use the same drive 
at the same time.

At 02:50 PM 5/31/2001 -0400, anthony.guzzi AT storability DOT com wrote:
>Curtis,
>
>   I'm sure you'll get a lot of responses on this, so consider my comments
>just part of the chorus.  If I understand SSO correctly, only the tape
>drives are shared, not the robot.  The robot is controlled by a single
>server which handles all tape mounts/unmounts.  In addition, this server
>also coordinates access to the tape drives.  It does this by running the
>'vmd' process (on a Unix system) in  'device allocation' (DA) mode.
>
>-- Tony Guzzi
>Solutions Engineer, AssuredRestore team
>Storability, Inc.
>118 Turnpike Road
>Southborough, MA 01772
>
>www.storabilility.com
>The Leading Provider of Automated Storage Assurance for the Enterprise
>
>
>
>
>veritas-bu-request AT mailman.eng.auburn DOT edu
>Sent by: veritas-bu-admin AT mailman.eng.auburn DOT edu
>05/31/2001 01:06 PM
>Please respond to veritas-bu
>
>
>         To:     veritas-bu AT mailman.eng.auburn DOT edu
>         cc:
>         Subject:        Does SSO Use SCSI Reserve/Release?
>Message: 5
>Date: Thu, 31 May 2001 09:55:36 -0700
>To: veritas-bu AT mailman.eng.auburn DOT edu
>From: "W. Curtis Preston" <curtis AT backupcentral DOT com>
>Subject: [Veritas-bu] Does SSO Use SCSI Reserve/Release?
>
>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.
>
>         <...... text deleted.    -AJG ......>
>
>---
>W. Curtis Preston
>Principal Consultant for Storage Designs, your storage experts
>Webmaster: http://www.backupcentral.com Phone: 760 631 7991
>
>
>_______________________________________________
>Veritas-bu maillist  -  Veritas-bu AT mailman.eng.auburn DOT edu
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---
W. Curtis Preston
Principal Consultant for Storage Designs, your storage experts
Webmaster: http://www.backupcentral.com Phone: 760 631 7991