[ADSM-L] SV: [ADSM-L] TSM handling of already compressed files
2010-05-14 02:59:46
I'm not sure I got your question right, but...
> I found out with some experimentation that
>TSM would take twice as long to backup a 60 GB compressed file as
>a 60 GB uncompressed file.
- A LTO2 tape drive can write data at 40Mbyte/s.
- A LTO2 tape drive can do hardware compression. Assume it does 2to1.
If you send a 400Mbyte uncompressible file (already compressed) it will write
the data in 10 seconds.
40MB/s on the fibre/scsi , 40MB/s to the tape and 400Mbyte goes to tape.
If you send a 400Mbyte 2to1-compressible file it will write it in 5 seconds.
80MB/s on the fibre/scsi , 40MB/s to the tape and 200Mbyte goes to tape.
It is normal that a compressed file of the SAME SIZE as an uncompressed file
takes twice as long to backup.
/Anders Räntilä
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RÄNKAB - Räntilä Konsult AB
Klippingvägen 23
SE-196 32 Kungsängen
Sweden
Email: Anders AT Rantila DOT com
Phone: +46 701 489 431
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