I have time as a vendor and a user.  Compression is very dependent on your 
data.  Plan on a 1.6:1 compression ratio as an average for budgeting purposes.  
Companies that do mass mailings skew the numbers up to a 9:1 ratio and the 
vendors average this to be a 3:1 ratio.

By the end of the day, it is simple math.  Use your goodies directory and 
available_media scripts to do math on full tapes to determine your companies 
compression ratio.

I have never failed with a 1.6:1 ratio.  It appears low, but is usually 
accurate for most shops.

Brian

-----Original Message-----
From: veritas-bu-admin AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Sto Rage© 
Sent: Thursday, April 07, 2005 6:26 PM
To: Jerry
Cc: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] compression calculation


isn't that cutting it too thin? Esp. now with costs of media being so
low. Unless you are talking of 000's of tapes.
 I'd use the basic tape capacity to calculate the tapes needed to be
safe. I have been burnt before by using compression numbers to
calculate tapes required. When jobs fail ( they do very often) you end
up having chunks of space used up on tapes thats un accounted for.
Whatever compression you gain gets offset by failed jobs, bad tapes
etc.
- my 2 cents.


On Apr 7, 2005 11:29 AM, Jerry <juanino AT yahoo DOT com> wrote:
> I'm trying to estimate how many tapes to purchase for
> a backup project.  Is there a way to tell the
> compression ratio I'm getting with hardware
> compression?  I have some backups of various systems
> but unless they are all the same type of backup and
> the tape is full, I'm not sure how to calculate it.
> 
> Jerry
> 
> 
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