On Monday 14 March 2005 10:14, Mark Lidstone wrote:
>Ooops.  Answering my own question.  I had a limit on the amount of
> space to use on the holding disk - Just increased it, so that
> should sort it.
>
>Righto, have turned off hardware compression (using "mt -f /dev/nst0
>compression 0"), changed my tapetype (see below) and, as I said,
>increased the size of my holding disk.  I will keep an eye on this
>tonight.

You have one other problem with that.  The state of the hardware 
compression is stored in a hidden header on the tape, and it will be 
turned on against your will during the tape drives tape recognition 
phase.

To cancel it for real, one must
rewind it
dd the label block out to a scratch file
rewind it
set the compression off with mt (do both variations)
dd the scratch file back to the tape, but this time use the rewinding 
device to do it so that the closing of the path at the end of the dd 
write will force a rewind, and that in turn will force the drive into 
a buffer flush since its now dirty, thereby resetting that hidden 
compression flag.

rewind it again & check with amcheck, should be ok.

Or, you can dd about 10 megs from /dev/zero to the non-rewinding 
device after writing the label block back, which will eventually 
force a buffer flush/write, doing the same thing in terms of 
resetting the compression flag in the tape header.

What I'd do I think, is write a script to do this, and run an amcheck 
to make sure the right tape is loaded before doing this, then have 
cron run this script about half an hour before the main amanda run.  
That way, you won't have destroyed any backups doing all that until 
the same day the tape is to be reused anyway.  Once the tapecycle has 
been used up and all tapes are set to off, then kill the crontab 
entry as its just one more pass on the tapes leaders, and a DDS tape 
dies quick enough as it is.

I hope this helps.

-- 
Cheers, Gene
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