The whole compression issue has always confused the hell out of me (no
certification here :-). Does 200-400 mean
"200-native-,-400-if-we-hardware-compress-as-we-stream-to-tape"?
Sometimes the client may also compress? I think salespeople over the
years have greatly abused this x-2x tape cartridge capacity thing to
their advantage - you can always double up because nobody knows what
you're talking about anyway.
And you mean LZ (Lempel-Ziv) algorithm, don't you :-?
-------------------------------------------
Willem Roos - (+27) 21 980 4941
Per sercas vi malkovri
> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]
> On Behalf Of Christo Heuer
> Sent: 16 April 2004 09:26
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: LTO tape cartridge(200GB/400GB) stores data 500GB+.
>
>
> 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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