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
1.5:1.
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
>tape.
>
>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
>NIBCO, Inc
>
>-----Original Message-----
>From: Chandrashekar, C. R. (Chandrasekhar)
>[mailto:cr.chandrashekar AT TIMKEN DOT COM]
>Sent: Thursday, April 15, 2004 11:51 PM
>To: ADSM-L AT VM.MARIST DOT EDU
>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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