Seagate STT20000A - Problems with compression

  • Thread starter Thread starter David J Edgar
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David J Edgar

Hi,

I've got a problem using hardware compression with a Seagate STT20000A IDE
Travan TR-5 tape drive.

I am using the backup program that is native to Windows 2000 Server and
can't get more than 10GB on a tape. These tapes should handle up to 20GB of
data if compressed. I have selected the 'use hardware compression if
available' option but the backup fails when 10GB has been written.

Has anybody else had this problem?

Seagate STT20000A (Firmware 8a51), Windows 2000 Server (SP4), Windows
Backup.

Dave.
 
In comp.sys.ibm.pc.hardware.storage David J Edgar said:
Hi,
Click to expand...
I've got a problem using hardware compression with a Seagate STT20000A IDE
Travan TR-5 tape drive.
Click to expand...
I am using the backup program that is native to Windows 2000 Server and
can't get more than 10GB on a tape. These tapes should handle up to 20GB of
data if compressed. I have selected the 'use hardware compression if
available' option but the backup fails when 10GB has been written.
Click to expand...
Has anybody else had this problem?
Click to expand...
Seagate STT20000A (Firmware 8a51), Windows 2000 Server (SP4), Windows
Backup.
Click to expand...

There is a mathematical limit to compressibility, called entropy.
You cannot compress better that the entropy contained, no matter what
algorithm. In practice, already compressed data can usually not
be compressed further. That includes video and audio that is
compressed. Since hardware compression can use little memory, it
usually does significantly worse than software compression tools.
It sometimes even enlarges pre-compressed data.

Arno
 
Arno Wagner said:
In comp.sys.ibm.pc.hardware.storage David J Edgar




There is a mathematical limit to compressibility, called entropy.
You cannot compress better that the entropy contained, no matter what
algorithm. In practice, already compressed data can usually not
be compressed further. That includes video and audio that is
compressed. Since hardware compression can use little memory, it
usually does significantly worse than software compression tools.
It sometimes even enlarges pre-compressed data.

Arno
Click to expand...

Thanks, but my problem is that no compression operation is attempted!

Dave.
 
Thanks, but my problem is that no compression operation is attempted!
Click to expand...

How do you know that? Just because it fails after 10GB does not mean
it does not try to compress. Or is there some other way you can tell?
If your data is pre-compressed, there is no way in this universe
you can get any significant compression on it.

Maybe it tries to compress but does not succeed and therefore writes
the data uncompressed.

Arno
 
Arno Wagner said:
In comp.sys.ibm.pc.hardware.storage David J Edgar


How do you know that? Just because it fails after 10GB does not mean
it does not try to compress. Or is there some other way you can tell?
If your data is pre-compressed, there is no way in this universe
you can get any significant compression on it.

Maybe it tries to compress but does not succeed and therefore writes
the data uncompressed.

Arno
Click to expand...
Check to see if your drive is already compressed. If it is, you will not
get compression on the tape
 
Hi,

I've got a problem using hardware compression with a Seagate STT20000A IDE
Travan TR-5 tape drive.

I am using the backup program that is native to Windows 2000 Server and
can't get more than 10GB on a tape. These tapes should handle up to 20GB of
data if compressed. I have selected the 'use hardware compression if
available' option but the backup fails when 10GB has been written.

Has anybody else had this problem?

Seagate STT20000A (Firmware 8a51), Windows 2000 Server (SP4), Windows
Backup.
Click to expand...

This drive is not capable of harware compression. The circuitry is just
not there. You must use software compression to get >10GB per tape.

http://www.certance.com/products/CertanceDrives/STT220000A-RDT-TechSpec.html


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