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 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}' ); }
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