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тАО04-23-2009 02:33 AM
тАО04-23-2009 02:33 AM
DAT160 - negative compression ratio?
i am really confused. I have backed-up my scan archive to tape (~130 Gb subtotal) and soon noticed, that only 72 Gb fits on a 160* media. At the same time, Data Protector reports 78 Gb of native capacity.
After a short exploration in depth found that a 0.9:1 ratio is displayed for 2nd media part.
SW compression was turned off, in fact.
My question is divided into two major subjects:
1) It's really so? Data is 48 bit TIFF (uncompressed), all file sizes between 100 and 400 Mb, generally.
Another tape - JPEG & RAR - shows even 0.8:1
Device firmware is WP74
2) Do you have any "estimation" table (or a s/w tool) for different data types - DV AVI, for example, large (gigabyte) WAVEs, et.c.
DCLZ paper doesn't help
How is best to know when hardware compression needs to be turned off, and when it's not? In fact, should be rather tricky on incremental (raster & vector) backups...
Regards,
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тАО04-23-2009 04:09 AM
тАО04-23-2009 04:09 AM
Re: DAT160 - negative compression ratio?
HP's Library and Tape Tools ( www.hp.com/go/tape ) under the "Sys Perf" button, will do a read of a filesystem and report on compressibility.
Liberty breeds responsibility; Government breeds dependence
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тАО04-29-2009 05:07 AM
тАО04-29-2009 05:07 AM
Re: DAT160 - negative compression ratio?
But passing large TIF files is very slow. Really slower, than a small ones to be honest...
Compare - 220 Mb/s falls to 116 on a 72 media.
(and Is a throughput an indirect mark of a file compression ratio?)
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тАО04-29-2009 05:09 AM
тАО04-29-2009 05:09 AM
Re: DAT160 - negative compression ratio?
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тАО05-27-2009 03:51 PM
тАО05-27-2009 03:51 PM
Re: DAT160 - negative compression ratio?
Large files do normally have good performance -- it's when you're backing up small files (less than 100K are slower; less than 10K can be painful) that performance starts to suffer.
Liberty breeds responsibility; Government breeds dependence