It depends on the actual type of data - take a 2Tb oracle db that is mostly
empty you will be getting a 90%+ compression ratio - so your LTO-2 cartridge
will show the capacity used as 2000Gb.
The typical ratio IBM used to qoute was 3-1 in recent years they changed
this to 2-1,
hence the 200-400 figure. The algorithm used for the comression is a
modified ZL algorithm - similar to the algorithm used for pkzip etc.
If you send already compressed data your tape usage will show 200Gig or
less - if you were getting negative compression ratios - data already
compressed can grow if comressed again.
So - there is no clear-cut answer - work on the native capacity(200G), and
everything else you get is a bonus.
Cheers
Christo
----- Original Message -----
From: "Chandrashekar, C. R. (Chandrasekhar)" <cr.chandrashekar AT TIMKEN DOT
COM>
To: <ADSM-L AT VM.MARIST DOT EDU>
Sent: Friday, April 16, 2004 7:50 AM
Subject: Re: LTO tape cartridge(200GB/400GB) stores data 500GB+.
> This is not a puzzle for me, Actually I want to know how much data it can
> compress, Is there any one using same tape library. Which helps to
estimate
> the total storage capacity.
>
> Just to know how much percentage of compression in 3583L23 library using
> 3580ULTGen2 drive.
>
> Thanks,
> c.r.chandrasekhar
>
> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]On Behalf Of
> Christo Heuer
> Sent: Friday, April 16, 2004 10:51 AM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: LTO tape cartridge(200GB/400GB) stores data 500GB+.
>
>
> Hi,
>
> I see you are a Tivoli certified consultant (TSM) - maybe they missed that
> part in
> the certification exam - why don't you read up on compression - if this
> puzzles you
> I'm sure plenty other things will confuse the hell out of you.
>
> Christo
> ----- Original Message -----
> From: "Chandrashekar, C. R. (Chandrasekhar)" <cr.chandrashekar AT TIMKEN DOT
> COM>
> To: <ADSM-L AT VM.MARIST DOT EDU>
> Sent: Friday, April 16, 2004 6:51 AM
> Subject: LTO tape cartridge(200GB/400GB) stores data 500GB+.
>
>
> > Hi,
> >
> > Just for clarification, I'm using LTO-Ult tape cartridge having capacity
> of
> > 200GB/400GB, Tape library 3582L23 with two 3580-LTOG2 drives with
firmware
> > 38D0, and devclass was defined with device-type=LTO and Format=ULTRIM2C.
> Now
> > the tape is storing more then 500GB of data, Is it normal behavior.
> >
> > Thanks,
> > CRC,
> >
> > C.R.Chandrasekhar.
> > Systems Analyst.
> > Tivoli Certified Consultant (TSM).
> > TIMKEN Engineering & Research - INDIA (P) Ltd., Bangalore.
> > Phone No: 91-80-51362222.
> > Email:cr.chandrashekar AT timken DOT com.
> >
> >
> >
> >
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