When using multiple media server there is a centralized catalog for the
media on the Master (vsnDB). The vsnDB tracks all tapes that are available.
There is also a mediaDB on each media server. The mediaDB tracks what tapes
that system is currently using.

In your case it b/c the systems are on the same library I can understand the
frustration. But in a distributed environment that has many libraries it is
extremely useful. Are you using a scratch pool? This will allow the system
to grab any tape from the free tape pool and assign it. If that tape is
assigned to a media server, chances are that it is going to need that tape
again.

In the event of a restore it will first attempt to go through the original
media server. However you can have it go through any media server connected
to the same library. In other words they will be able to access a tape
originally used by another media server.

The media server can be migrated from one to another. With a few steps you
can take backups done by one system and move them to another system if you
need to.

Skip


-----Original Message-----
From: George Roper [mailto:backup_user AT hotmail DOT com]
Sent: Thursday, March 16, 2000 5:32 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Storage Units


Hi Patrick,

Thanks for your thoughts.

Unfortunately I wish it were as simple as this :o(

I definately have only ONE Volume DataBase. This is stored on the host that 
controls the robot.

I believe the problem lies with the fact that NetBackup needs to maintain 
it's own distributed Media Database. Each server connected to drives 
maintains it's own Database. I can prove this by running an bpmedialist 
-summary, this lists each Slave's Media database.

Once a slave server writes to a tape, it exclusively owns it by making an 
entry for the Volume ID in it's Media database. Once owned, a volume cannot 
be used by any other host until returned to the Volume manager through 
expiry. I believe it is this behaviour that is this root cause of my 
problem.

Can any-one confirm/correct my understanding/observation or answer my
operational questions:-

   o Is this behaviour correct?
   o Is there a way of modifying it so that one SU can gain access to
     the other's volumes?


Regards,

George
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