For my own info, I will use the available_media script
to determine an overall compression ratio for my
company as suggested (good idea).

Also a good idea, I'll use the raw size of the tape as
the estimate.  You're right, it's so cheap it makes
sense to just assume no compression (or very little). 
I have Terabytes of data that is already compressed
when it hits tape, so it will throw off the average
anyway.

--- Sto Rage©  <netbacker AT gmail DOT com> wrote:
> 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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