| Author |
Message |
Toolmann
Guest
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 Posted:
Fri Jan 28, 2005 5:11 am Post subject:
HP StorageWorks AIT2 50/100GB |
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I am unable to achieve much more then 1.2:1 compression ratio on my
backups. I run Windows 2000 and use Veritas Backup Exec 9.1 and a
mixture of Compaq 50/100 and Sony SDX2-50C 50/100 tapes. I have tried
compression settings of "hardware first, then software" as well as
"software only".
Any help would be greatly appreciated. |
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Maxim S. Shatskih
Guest
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| Posted:
Fri Jan 28, 2005 5:43 am Post subject:
Re: HP StorageWorks AIT2 50/100GB |
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Maybe you backup uncompressable data?
--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com
"Toolmann" <davidrearly@hotmail.com> wrote in message
news:1106871115.858181.283940@z14g2000cwz.googlegroups.com...
| Quote: | I am unable to achieve much more then 1.2:1 compression ratio on my
backups. I run Windows 2000 and use Veritas Backup Exec 9.1 and a
mixture of Compaq 50/100 and Sony SDX2-50C 50/100 tapes. I have tried
compression settings of "hardware first, then software" as well as
"software only".
Any help would be greatly appreciated.
|
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Toolmann
Guest
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| Posted:
Fri Jan 28, 2005 6:32 pm Post subject:
Re: HP StorageWorks AIT2 50/100GB |
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I am backing up a mixture of MS Office documents, PDF's and pictures.
I think I should expect a little better compression such as 1.5:1 but
maybe I am wrong. |
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RPR
Guest
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| Posted:
Fri Jan 28, 2005 10:26 pm Post subject:
Re: HP StorageWorks AIT2 50/100GB |
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Compression on tape drives is a lot harder than software compression a
la ZIP. It has to be done in real time, and every block has to be
compressed separately so you can access it individually. As a result,
the compression factors are lower than what you're used to. |
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Maxim S. Shatskih
Guest
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| Posted:
Fri Jan 28, 2005 11:28 pm Post subject:
Re: HP StorageWorks AIT2 50/100GB |
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PDF is very bad in terms of compression.
--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com
"Toolmann" <davidrearly@hotmail.com> wrote in message
news:1106919138.812278.292640@z14g2000cwz.googlegroups.com...
| Quote: | I am backing up a mixture of MS Office documents, PDF's and pictures.
I think I should expect a little better compression such as 1.5:1 but
maybe I am wrong.
|
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| Back to top |
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Maxim S. Shatskih
Guest
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| Posted:
Fri Jan 28, 2005 11:33 pm Post subject:
Re: HP StorageWorks AIT2 50/100GB |
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| Quote: | Compression on tape drives is a lot harder than software compression a
la ZIP. It has to be done in real time,
|
Yes, and also memory is usually scarse. You cannot run PPM algorithm on a
drive, and I even have doubts you can run BWT there (due to unpredictable time
degradation on "bad" data). So, only LZ, which is the bad algorithm for any
well-compressable data.
--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com |
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RPR
Guest
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| Posted:
Tue Feb 01, 2005 5:42 am Post subject:
Re: HP StorageWorks AIT2 50/100GB |
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PPM or BWT sure would be cool but I don't think anybody has designed
silicon for them (yet?). LZ seems like the only game in town today. |
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Anton Rang
Guest
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| Posted:
Wed Feb 02, 2005 10:20 pm Post subject:
Re: HP StorageWorks AIT2 50/100GB |
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"Maxim S. Shatskih" <maxim@storagecraft.com> writes:
| Quote: | Compression on tape drives is a lot harder than software compression a
la ZIP. It has to be done in real time,
Yes, and also memory is usually scarse. You cannot run PPM algorithm on a
drive, and I even have doubts you can run BWT there (due to unpredictable time
degradation on "bad" data). So, only LZ, which is the bad algorithm for any
well-compressable data.
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The ALDC (Adaptive Lossless Data Compression) algorithm is an ECMA standard:
http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-222.pdf
It uses a history buffer no larger than 2K, so even as LZ compressors go, it's
very modest.
-- Anton |
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