On Fri February 28 2003 10:18, Damon LaCaille wrote:
>All:
>
>Thanks to Jay Lessert, I was able to create a new tape type on a
> Solaris 9 Sun E450 with an HP JetStore HP-C1533 DDS-2 tape drive.
> Here is the configuration output for it using the /dev/rmt/0n
> tape device
>
>define tapetype HP-C1533 {
> comment "just produced by tapetype program"
> length 3275 mbytes
> filemark 0 kbytes
> speed 430 kps
>}
Ouch, from this, the drives compression is turned on. The various
tapetype utilities all use /dev/urandom as the data source for the
written data, and the random data from /dev/urandom is so
uncompressable it will be expanded by the hardware compressor in
the drive, in this case it looks as if the expansion was about 700
megabytes.
Amanda's use of gzip can usually beat the hardware compression,
often by large amounts. So we, as a group have been recommending
that any hardware compression be turned off, and then use one of
the compressing dumptypes for those disklist entries that will
compress well. Obviously a directory full of *.gz or *.bz2 stuff
won't compress so use a non-compressing dumptype for those.
Be aware that one of these tapes has a hidden header that records
the status of the hardware compressor when the tape was written.
This has the effect of that tape causing the compressor to be
turned back on during the tape recognition scan when the tape is
inserted regardless of the state of the dip switch setting.
In order to "uncompress" such a tape, one must use the appropriate
mt command to shut it off on a fully rewound tape, then force a
buffer flushing write to the tape by writing about 2x the drives
rated buffer in one swell foop. This needs to be done to every
tape thats been written to so far, including the labeling
operations. As this will destroy the data on that tape, I'd make
it into a script and run it a few minutes before the real backup is
done, using a root crontab entry.
The script should loosely resemble this, using the rewinding device:
mt -f device rewind
# save the tapes label
dd if=device of=./scratch bs=32k
# now turn off the compression
mt -f device compression -1 or off, depends on your mt, chk manpage
# now force a buffer flush, this will take a few minutes
dd of=device if=/dev/zero bs=32k count=1000000
# now restore tape label so amcheck is happy
dd if=./scratch of=device
Now, in your case it appears that you would be using more than one
tape and or drive per session, and while I do have a changer, I've
never had to deal with that so I don't have any ready made 'canned'
answers as to how to go about this for more than one tape or drive.
If rotating drives then just dup the script for each device, but
changeing tapes is a bit beyond what I've done if you need to treat
more than one tape per drive just before each backup session.
>Hope this helps. My actual setup is a SpectraLogic 10000 BullFrog
> with 60 slots and (4) HP-C1533 tape drives. I'm hoping to get
> all 4 tape drives to use the carousel tape library, but it may be
> wishful thinking. Any tips would be greatly appreciated. The
> number of available programs (both supported and unsupported)
> seems a little overwhelming to try and figure out, but hopefully
> one of them will work.
>
>Thanks,
>Damon
>
>
>-----Original Message-----
From: Damon LaCaille
>Sent: Thursday, February 27, 2003 11:43 AM
>To: 'amanda-users AT amanda DOT org'
>Subject: Question about tapetype program
>
>
>Hi everyone,
>
>I am configuring an HP JetStore 6000 C1533 DDS-2 tape drive. I
> have 4 of them in a SpectraLogic 10000 (BullFrog) tape library,
> with 60 slots.
>
>I am running tapetype like this:
>
># ./tapetype -e 4g -f /dev/rmt/0bn -t "HP JetStore 6000 C1533"
>
>It's been running for about 90 minutes and I'm estimating it's
> about 40% of the way done.
>
>My question: Should I have used the compression device
> (/dev/rmt/0mbn or /dev/rmt/0hbn) instead of the non-compression
> device? I've noticed a few posts that reference compression
> devices when running tapetype, but the docs say to use the
> regular device.
>
>Thanks for the help!
>
>Damon
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
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