On Tuesday 04 October 2005 03:20, Sven Rudolph wrote:
>Gene Heskett <gene.heskett AT verizon DOT net> writes:
>> On Thursday 29 September 2005 17:06, Christopher Davis wrote:
>>>The drive doesn't have any dip switches - I even took the drive out of
>>> the encosure and couldn't find anything.
>>>
>>>I copied the wrong mt command over -
>>>
>>>Where I'm at now is looking at stinit ant the /etc/stinig.def file to
>>> create a /dev/nst0l device which disables compression - I'm in the
>>> middle of another test right now and can't try it out just yet - but
>>> if this works for me I'll send it to the list. We have a ton of
>>> these Sun SDLT 220 drives floating around and want to use them.
>>>
>>>
>>>I ran some tests using hardware compression and wasn't impressed with
>>> the results so I'm trying it with it off.
>>
>> Be aware that for many tape formats, the compression status is saved
>> in a hidden header of the tape, so that once its been written in the
>> compression on mode, that will be restored to on when the
>> tape is loaded regardless of your wishes unless specifically disabled.
>>
>> I had a script at one time that turned these flags off, and it looked
>> something like this:
>>
>> #!/bin/sh
>> mt -f /dev/nst0 rewind
>> dd if=/dev/st0 of=./scratch count=1
>> mt -f /dev/nst0 defcompression off (or 0 depending on your mt)
>> mt -f /dev/nst0 compression off (or 0 depending on your mt)
>> dd if=./scratch of =/dev/nst0
>> dd if=/dev/zero of=/dev/st0 count=(your drives buffer size plus 1)
>> dd if=/dev/st0 (should show the tape label unchanged from ./scratch)
>>
>> Note use of /dev/st0 for its automatic rewind in places. simplifies
>> the script..
>
>I use a bit less magic (it is enough to overwrite the first block on
>tape (SDLT220/SDLT600)); see below. And in my do_amdump (a wrapper
>around amdump) I have:
>
> /usr/sbin/amtape DailySet1 taper
>
> /usr/local/bin/erase_tape /dev/st2
>
>(Some time ago we had a discussion on having a hook to run a command
>when a tape is to be written, but we didn't find a good solution.)
>
> Sven
>-----
>host:~# cat /usr/local/bin/erase_tape
>#!/bin/sh
>
>tapedev=$1
>labelfile=$(tempfile)
>
>mt -f $tapedev rewind
>
>dd if=$tapedev of=$labelfile bs=32k count=1
>
>sudo unset_tape_compression $tapedev
>
>dd if=$labelfile of=$tapedev bs=32k count=1
>
>
>
>host:~# cat /usr/local/bin/unset_tape_compression
>#!/bin/sh
>
>tapedev="$1"
>
>case "$tapedev" in
> /dev/st[0-9]) ;;
> *)
> echo "invalid device $tapedev" >&2
> exit 1
>esac
>
>mt -f $tapedev datcompression off
Neat, and with better housekeeping than some of my hacks have had. I
tend to scratch the itchiest place first and when thats fixed, the
rest just get a lick and a promise. Sometimes its a year before I
get back to the promise :)
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.35% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.
|
