> -----Original Message-----
> From: Prather, Wanda [mailto:PrathW1 AT CENTRAL.SSD.JHUAPL DOT EDU]
> Sent: Wednesday, November 18, 1998 11:29 PM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: Client Compression Rate
>
>
> I agree with Andy, there is no guaranteed way to tell.
>
> I have worked with several different ADSM installations. As
> Andy said, text
> data compresses well, executable files don't. If you have a
> wide variety of
> client machines, say a mixture of Unix and Windows machines,
> a mixture of
> file servers, print severs, desktops, etc., on average you
> will probably see
> slightly better than 2 for 1 compression, but not 3 for 1.
>
> If your client machines are all the same configuration, say
> all Oracle data
> bases, or all mail servers, then the best bet, as Andy said,
> is to try one
> and see what you get.
>
> However, let me add another 2 cents worth here: when planning library
> capacity, the mistake people usually make is assuming that if
> they have 200
> GB of data to back up, they need 200 GB of tape capacity in
> the library.
> YOU WILL NEED MORE THAN THAT.
>
> Over time your storage pool tapes will become fragmented as
> old versions of
> data become invalid. If your reclamation threshold is set
> at, say, 70%,
> your tapes will all have different amounts of VALID data
> between 100 and
> 30%. So you will need enough library capacity to account for
> the fact that
> not all tapes are 100% full.
And that is not the only thing, what about copy pool's?
And database backup's for the ADSM database itself?
Regards Frans Bijma
>
> ***************************************************************
> Wanda Prather
> The Johns Hopkins Applied Physics Lab
> 443-778-8769
> wanda_prather AT jhuapl DOT edu
>
> "Intelligence has much less practical application than you'd think" -
> Scott Adams/Dilbert
> ***************************************************************
>
>
>
>
> > -----Original Message-----
> > From: Andy Raibeck [SMTP:storman AT US.IBM DOT COM]
> > Sent: Wednesday, November 18, 1998 1:46 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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