Thanks for the info. I figure I would go with the 2:1 rate when ordering
tapes. It is better to have too many then not enough. Thanks again.
> ----------
> From: Andy Raibeck[SMTP:storman AT US.IBM DOT COM]
> Reply To: ADSM: Dist Stor Manager
> Sent: Wednesday, November 18, 1998 12:46 PM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: Client Compression Rate
>
> Hello Linda,
>
> It is almost impossible for me to tell you what the ADSM compression
> ratios would be for your data. This is because compression ratios
> vary, depending on the type of data being compressed. For instance,
> text files compress very nicely while files that are already
> compressed will not compress very well; in fact, they may even grow!
>
> Even your 3575 won't realize 3:1 compression on data that is already
> compressed. A very popular question goes something like, "IBM says
> I should be getting 30 GB on a 10 GB tape with 3590 compression, but
> my tapes are getting full and they have only 9 - 11 GB of data on
> them. What am I doing wrong?" The answer to this is that they are
> probably backing up a lot of data that is already compressed (like
> .ZIP files) or they are using client compression.
>
> ADSM uses an industry standard compression algorithm so if I had to
> give a number, I'd say 2:1 to 3:1, depending on the type of data
> you are backing up. Again, though, your mileage may vary! :-)
>
> I would recommend backing up one or two systems that are
> representative of your clients and see what kind of compression
> ratios they yield. Then you can try to extrapolate from there.
>
> Sorry I can't be more accurate.
>
> Regards,
>
> Andy
>
> Andy Raibeck
> IBM Storage Systems Division
> ADSM Client Development
> e-mail: storman AT us.ibm DOT com
> "The only dumb question is the one that goes unasked."
>
> This is probably directed more to IBM but I would appreciated it if any
> one
> has any info or can point me in the right direction. (I feel like I am
> going around in circle)
>
> I still have questions concerning the Client Compression Rate.
>
> Server: AIX 4.2.1 with ADSM 3.1.5
> Clients: NT ver 2.x.x
> NT ver 3.x.x
> Tape Library: 3575-L24
>
> I have client compress on due to network issues. I need to est. the
> amount
> of tapes needed for roughly 600 PCs. My question is what kind of
> compress
> rate can I expect using Client Compress. (I am aware of the compression
> ratio for the 3575 - raw 3:1). I placed a service call but so far all
> they
> have told me is the capacity of the library. HELP! If I get an answer
> back
> from IBM, I will post it. Thank in Advanced.
>
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