There is no set optimum setting for multistreaming or for multiplexing.
It is something you have to keep adjusting as you add/delete/upgrade
servers.

The best thing I can tell you for immediate results is if possible
put Gbit in your media servers.  Your current environment (assuming
the master is also a media server) is 3x100Mbit worth of traffic at
a time no matter how many tape drives you have/use.  300Mbit/8 = 
~37.5MB/sec.  Since the SDLT's are going to be at least 11 MB/sec
uncompressed (depeneding upon the model) you cannot drive all the
drives full speed.  Putting Gbit into the media servers will change
to 3000Mbit/8 = 375MB/sec.

There are a few additional things to cover such as speed of media
servers, memory, load on the system, speed of servers with largest
concentration of data, etc.

This is by no means a final answer, but should be a good starting point.

Good Luck,
Ken
--
Sr Unix Admin
Accor North America
ksibley AT accor-na DOT com
469-737-3370



-----Original Message-----
From: Ashraff Khan [mailto:AshraffK AT teletext.co DOT uk]
Sent: Friday, June 11, 2004 4:29 AM
To: 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: [Veritas-bu] FW: Multistreaming/Multiprexing




We are currently running Veritas NetBackup V3.4 for our centralised backup
solution and are experiencing problems with the every expanding backup
windows which is currently taking around 12hrs to backup 750GB of data.
Our systems spec:
2 x Qualstar TLD6460 sixty slots and 2 x SDLT drives in each library. 
1 x Master and 2 x Media servers controlling each library.
We are currently backing up a total of 70 servers on the network which are
all connecting through 100MB full-duplex switched network.
The total data being backed up on a daily basis is around 750GB, but total
data in library is around 10TB because it takes so long to duplicate the
data.
We are currently holding data with retention period of 1 month.
Questions:
1.      How can we reduce the backup windows considerably?
2.      How can we reduce the retention period?
3.      How can we speed up the tape duplication process?
4.      How can we utilise multistreaming and multiplexing to reduce backup
window?
5.      What is the optimum setting for multistreaming and multiplexing in
our environment?
6.      What is the total throughput of the SDLT drives i.e. MB per sec.
7.      How can we utilise the two drives in the library to double the
throughput.


Thanks
Ash.


Ashraff Khan 
Principal Systems Project Manager 
IT Systems
Teletext Ltd.