Re: LTO tape cartridge(200GB/400GB) stores data 500GB+.

2004-04-17 05:59:58
Subject: Re: LTO tape cartridge(200GB/400GB) stores data 500GB+.
From: Roger Deschner <rogerd AT UIC DOT EDU>
Date: Fri, 16 Apr 2004 23:22:46 -0500
This varies greatly with the data, of course. I'm seeing compression
ratios of 4:1 with email, which is mostly plain text with a lot of blank
space characters. MIME attachments usually compress 2:1. Many binaries
are already compressed, such as jpeg images, and do not compress any
further. But on the general mix of client-owned data, I see more like

Do client compression. They have more spare CPU cycles than your server
does, and this also saves your network bandwidth. It also conserves
space in your online disk storage pools. A study done by SPSS Inc. a few
years ago showed that data compression was essentially free. The
processor time it took to do the compression in a program's internal
storage was less than the additional processor time it would have taken
to handle the I/O for writing the larger, uncompressed file out. Just be
prepared for that 200/400GB tape cartridge to hold only 200GB.

Roger Deschner      University of Illinois at Chicago     rogerd AT uic DOT edu

On Fri, 16 Apr 2004, Tom Kauffman wrote:

>That depends -- on the data and on the client.
>I've got LTO-1 (100/200) GB tapes and drives. MS-Exchange Infostore backups
>are compressed on disk and not decompressed by the client for backup - and I
>get full tapes at 101 GB. On the other hand, my SAP/R3 (Oracle) database is
>not compressed on the client -- and I get between 485 GB and 521 GB per
>So - you should get at least 190 to 200 GB per tape on the LTO-2; you MAY
>get considerably more than 400 GB. We'll be going LTO-2 in five months, and
>I'm looking forward to seeing how much SAP database I can fit on one tape.
>Tom Kauffman
>-----Original Message-----
>From: Chandrashekar, C. R. (Chandrasekhar)
>[mailto:cr.chandrashekar AT TIMKEN DOT COM]
>Sent: Thursday, April 15, 2004 11:51 PM
>Subject: LTO tape cartridge(200GB/400GB) stores data 500GB+.
>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.
>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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