On Thu May 1 2003 03:40, Paul Bijnens wrote:
>Greg Troxel wrote:
>>[dropping list]
>>
>>Thanks. Some of that is ancient history, and I have dds3 drive
>> that I dip-switched to no compression.
>>
>>Do you mean to say that a tape that was once written compressed
>> will be (re)written compressed even on a drive jumpered for no
>> compression?
>
>When you insert a tape in a drive, and read it, the drive adjusts
> itself to the settings of that tape. That means that if it was
> written with hardware
>compression the drive sets itself accordingly, even if it was set
> to no hw compr.
>This is exactly what happens with an Amanda tape that was labeled
> with hw compr.
>Amanda verifies the label, and thus implicitly sets hw compr if
> the label was written as such.
>To get rid of hw compr tapes, you have to insert the tape, execute
> the command
>to disable hw compr, and write to the tape WITHOUT first reading
> it. Amlabel first reads the tape, so you cannot use that one
> (maybe we could add an
>option to amlabel to do just this, but it is a dangerous option!).
>Something like this works:
>
> $ mt compression off
> $ mt status
> (verify compression status and blocksize (0 = var, is
> best)) $ dd bs=32k count=10 if=/dev/zero of=/dev/your/tape
> $ amlabel YouConfig OLDLABEL45
> (probably add -f to force)
I use dd to extract the label block, turn the compression off, and
dd the label block back to the tape, all using the rewinding
version of the device. That way one isn't messing with the old
girls mind by calling amlabel, which in turn messes with the
tapelist order.
>I never investigated what happens if you set certain combinations
> of dipswitches
>and the above behaviour. It could be that wich the correct
> combination, you never
>ever write with hw compr.
>
>>You motivated me to look at my data more carefully, including
>>successful dumps.
>>
>>These produce input for xplot:
>>
>>function amanda-sizes-dds3-error { (echo double double;cat
>> OLD-*-dds3/log.* oldlog/log.* log.* |egrep 'INFO taper.*space' |
>> sort -n +5 | awk '{n=n+1;print ". " n " " $6}' ); } function
>> amanda-sizes-dds2-error { (echo double double;cat
>> OLD-*-dds2/log.* |egrep 'INFO taper.*space' | sort -n +5 | awk
>> '{n=n+1;print ". " n " " $6}' ); }
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
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by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.
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