Tape drive usage can be based on your storage unit.

If you have 10 tape drives but you have 2 storage units with 4 drives
each
That means at the most you will only use 8 drives.

So it could be that the storage units you are using are not set up to
utilize all the drives.

As to the fact that 2 different ones are avail.  Netbackup tries to use
the tape drives in a round robin kind of way so that each tape drives
gets used. Trying to even out the usage.  So first round of 8 drives
would use drives 1 - 8 but the second round might use 3 - 10.

Look at the number of drives in your storage units and see if you can
increase them any to use all 10 drives.


-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of
mcw012765
Sent: Monday, March 16, 2009 6:33 AM
To: VERITAS-BU AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Not all drives appear to be used


I am a Netbackup 6.5.2A user.  I currently have 100+ clients that I back
up on a daily basis (fulls and cumulative incrementals).  I have a
Sun/STK SL3000 tape library with 10 LTO-4 tape drives. My issue is with
tape drive usage.  I have multiplexing and multistreaming turned on for
all of my policies.  It appears that only 8 of the 10 drives are in use
at a time.  Also, it is not always the same 2 drives not in use.  

Any ideas on why this is?  As I write this, I have several jobs queued
saying that "required drives are in use", but there are 2 tape drives
available.

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