Simon, 

Multiplexing will not help you write "more" info to a tape. A tape can hold
a specific amount of data based on tape format and compression. Once it is
full, it is full. Using Multiplexing can help you use less tapes during a
backup run since more streams are filling up a single tape rather than
loading three tapes and writing to them, but NetBackup will continue loading
and using a tape until it is full, then it will move on to a new tape. 

Also, on other thing I wanted to point out about the bpexpdate command is
that it does NOT "erase" a tape it simply removes the NetBackup Catalog
reference to that tape and allows it to be overwritten. The data is still on
the tape until it is overwritten. The only reason I bring this up is for
security reasons. If you need to get rid of the data on the tape, you need
to bpexpdate it, then run a big magnet over it to wipe the data. 

Hope this all helps. 

dave

-----Original Message-----
From: WEAVER, Simon [mailto:Simon.WEAVER AT astrium-space DOT com] 
Sent: Monday, May 20, 2002 5:45 AM
To: 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: [Veritas-bu] Multiplexing

Firstly, Thank you all for your help with BPEXPDATE. I am glad I am getting
this right now :)

I have one small question about Multiplexing. On the Netbackup PDF's (which
is what I am using) it says you can specify the number of jobs that can
multiplex to a single tape drive! (Words to that effect).

My question is this: I have a backup policy with 8 clients listed. Within
this backup policy I have specified to backup All Local Drives for these 8
clients. I want to use as less tapes as possible (I use 100GB HCART Tapes).
If I increase this Multiplexing number, does it mean that more data will be
written to a single drive in a tape?

We use an ADIC Scalar 100 which consists of 3 tape drives. Because I have no
more slots available to place blank tapes, I was kind of hoping that using
this Multiplexing option will help retain more data on a single tape!

Am I right, or am I reading this incorrectly.!

Thank you

Simon Weaver
NT Domain Administrator
Ext. 5544
Tel: 02392-705544 (Direct Dial)
Simon.Weaver AT Astrium-Space DOT com

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