On Monday 24 November 2003 03:46, Martin Oehler wrote:
>Hi!
>
>Am So, 2003-11-23 um 14.16 schrieb Gene Heskett:
>> There is amtapetype, which will destructively write the tape till
>> it hits EOT, and will tell you the size it found.  See the man
>> page for running options to help speed it up as its quite slow,
>> doing 2 passes.
>
>SYNOPSIS
>       amtapetype  [-h]  [-c]  [-b  blocksize]  [-e  estsize] [-f
>       tapedev] [-t typename]
>
>Hmm, the only option that sounds like it could speed up the process
>is blocksize. Does anyone know a good value for this?

I would use that only if you are using a non-std blocksize, which I 
am, rather than the default 512 byte, I'm using 32768 for reasons 
other than any percieved speed advantage.  There isn't any as long as 
the drive is streaming.  But changing this is an mt command I think, 
done ahead of time.  I do mine in /etc/rc.d/rc.local at boot time.  
However, there must be a tape in the drive or that fails later for 
amanda.

>Is the test faster the bigger I choose this value? (so 1 would take
>about 1 GB)

The -e size option allows it to march right along on the first pass, 
so if you have an 80G tape (see the options defines for estsize 
syntax) you can pass this to it.  We're told that speeds up the first 
pass considerably.

Doing this to a tape also should tell you whether or not the drives 
internal compression is in use, which for amanda, should be turned 
off as that hides the true size of the tape from amanda.  Amanda 
counts bytes sent to the drive after any gzip is applied, and if the 
drives compressor is on, the data normally will grow slightly and 
amanda may hit EOT thinking it still has 10-15% of the tape left.

Turning off the drives internal compressor can be a problem child too, 
and must be done external to amanda.  However I've worked out a 
script that saves the tapes label info, turns the compressor off, and 
re-writes the label.  The programming switches on the drive must also 
be set to the off position before doing this, and on some drives, you 
will have to powercycle the drive to get it to re-read the switches 
state.  Since the switches aren't that accessable normally, the 
machine powerdown done to remove and access the drive will take care 
of that.

>Thanks in advance,
>Martin Öhler

Humm, do I recall that name from a decade or so back when I was 
running an amiga?

-- 
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz  512M
99.27% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com attornies please note, additions to this message
by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.