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Home > Archive > Data Storage > October 2006 > Sony Tape Drive Compression
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Sony Tape Drive Compression
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| Yoann Roman 2006-10-11, 1:15 pm |
| This group appears more suited to this question than comp.compression...
I have a Sony AIT-2 SCSI tape drive using 50/120 GB tapes and Retrospect
Backup 6.0. Sony's compression ratio is advertised as 2.6. The maximum I've
ever gotten on a tape using hardware compression is around 57 GB.
I realize compression is dependent on file type, and I am backup up a mix of
non-compressed and compressed files. But, out of curiosity, what have others
seen using this drive? Using a backup of an operating system drive (w/ no
user data) as a reference may make comparison easier.
Thanks,
--
Yoann Roman
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| Joshua Baker-LePain 2006-10-12, 1:14 pm |
| On 2006-10-11, Yoann Roman <yoann@cc.spam-bypass.gatech.edu> wrote:
> This group appears more suited to this question than comp.compression...
>
> I have a Sony AIT-2 SCSI tape drive using 50/120 GB tapes and Retrospect
> Backup 6.0. Sony's compression ratio is advertised as 2.6. The maximum I've
> ever gotten on a tape using hardware compression is around 57 GB.
>
> I realize compression is dependent on file type, and I am backup up a mix of
> non-compressed and compressed files. But, out of curiosity, what have others
> seen using this drive? Using a backup of an operating system drive (w/ no
> user data) as a reference may make comparison easier.
Conventional wisdom is that Sony's claims of 2.6x compression for AIT are
based on compressing a stream generated by 'cat /dev/zero'. ;) I've never
seen anywhere near 2x.
--
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University
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| I've also seen indications that when Sony OEMs AIT drives to others
such as Compaq that the firmware uses a different compression
algorithm, described as "the more reliable 2:1"
I had some tapes that I believe were in this 2:1 format a while back,
and my Sony drive couldn't read them, but a Compaq drive could. (These
were AIT3's)
Has anyone out there had any similar experiences?
Chris
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| Anton Rang 2006-10-19, 7:14 am |
| "Yoann Roman" <yoann@cc.spam-bypass.gatech.edu> writes:
> I have a Sony AIT-2 SCSI tape drive using 50/120 GB tapes and Retrospect
> Backup 6.0. Sony's compression ratio is advertised as 2.6. The maximum I've
> ever gotten on a tape using hardware compression is around 57 GB.
I have an AIT-1 (same compression algorithm). On a 35 GB tape, I typically
get 45-50 GB of backups, so roughly 1.3:1. This is on my home systems, so
a fair amount (50%?) of the data is compressed audio or images.
Anton
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