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тАО07-14-2009 09:31 AM
тАО07-14-2009 09:31 AM
Solved! Go to Solution.
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тАО07-14-2009 12:35 PM
тАО07-14-2009 12:35 PM
Re: HP Storageworks Dat 72 Tape full at 42
Pablo Alvarado Siles
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тАО07-14-2009 05:40 PM
тАО07-14-2009 05:40 PM
Re: HP Storageworks Dat 72 Tape full at 42
Different data is compressible different amounts. Did you scan your entire disk to get the 2.15:1 ratio? Exactly which test did you run?
Liberty breeds responsibility; Government breeds dependence
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тАО07-15-2009 08:05 AM
тАО07-15-2009 08:05 AM
Re: HP Storageworks Dat 72 Tape full at 42
Test results said "Data sent to DC: 65664 Kbytes, Data written to tape: 30508 Kbytes, Write compression ratio is 2.15:1."
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тАО07-15-2009 10:41 AM
тАО07-15-2009 10:41 AM
Re: HP Storageworks Dat 72 Tape full at 42
This test data is very highly compressible so you see this whopping 2.15:1 figure.
When backing up regular data of a general mix of different office files (texts, docs, spreadsheets, etc. you'll see more like 1.8 in practice.
When the backup contains lots of graphical files, JPGs, PNGs, PDFs, videos, etc. in most cases you're lucky to get higher than 1.0, many of these file formats are already so much compressed that no further compression is possible.
Have a look at the type of data you're sending to the tape; that should give you an indication what to expect.
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тАО07-15-2009 02:07 PM
тАО07-15-2009 02:07 PM
Re: HP Storageworks Dat 72 Tape full at 42
But what i am having trouble comprehending is why 42 gb = full on a 72 gb tape.
The tape can fit 36 gb compressed or uncompressed data? Where does my extra 6 gb come from? and why is it no more or less? Is only compressed data allowed on the tape or can both compressed & uncompressed be simultaneously?
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тАО07-16-2009 12:04 AM
тАО07-16-2009 12:04 AM
SolutionYou loose a bit in overhead.
Data is compressed while writing to the tape.
Compare when you create a ZIP or RAR from random data. If you do that for things like JPG or MPG files, then you may even end up with files that are larger than the original as also the compression process does require some overhead to recover the original data.