Re: Seagate STT20000A - Problems with compression

"Arno Wagner" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> In comp.sys.ibm.pc.hardware.storage David J Edgar
<[EMAIL PROTECTED]> wrote:
> > "Arno Wagner" <[EMAIL PROTECTED]> wrote in message
> > news:[EMAIL PROTECTED]
> >> In comp.sys.ibm.pc.hardware.storage David J Edgar
> > <[EMAIL PROTECTED]> wrote:
> >> > 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.
> >>
> >> 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
> >> -- 
> >> For email address: lastname AT tik DOT ee DOT ethz DOT ch
> >> GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25
338F
> >>   "The more corrupt the state, the more numerous the laws" - Tacitus
> >>
> >>
> >>
>
> > Thanks, but my problem is that no compression operation is attempted!
>
> 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
> -- 
> For email address: lastname AT tik DOT ee DOT ethz DOT ch
> GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
>   "The more corrupt the state, the more numerous the laws" - Tacitus
>
>
Check to see if your drive is already compressed.  If it is, you will not
get compression on the tape