ADSM-L

Sizing for a virtual tape library

2004-09-01 10:03:17
Subject: Sizing for a virtual tape library
From: "Thach, Kevin G" <KThach AT COVHLTH DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 1 Sep 2004 10:04:41 -0400
Greetings-

We are looking at purchasing an EMC CDL (virtual tape library), and I'm
trying to figure out exactly how much disk I'm going to need to meet my
requirements.

select sum(physical_mb) from occupancy where stgpool_name='<tapepool>'

Gives me ~62TB.  Is that number the compressed value, or the actual
value?  In other words, assuming I do no compression with the new setup,
would I be able to get by with ~62TB of disk?  Or would I need more?

I've read that compression is transparent to TSM since I'm doing
compression on my tape drives, so that number should represent what was
sent to the drives, correct?  It should therefore be the actual size of
the data before compression, right?

I did a search and found some past threads about this, but they confused
me even more!  =)

If someone could set me straight, I'd appreciate it.

Thanks,
Kevin

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