On Thursday 14 May 2020 01:32:05 Jon LaBadie wrote:
> On Wed, May 13, 2020 at 06:17:02PM +0200, Stefan G. Weichinger wrote:
> > Now look at this run of
> >
> > "amtapetype -b 128k /dev/nst0"
> >
> > with another tape, FUJI instead of HP:
> >
> > define tapetype LTO3-fuji {
> > comment "Created by amtapetype; compression disabled"
> > length 284180096 kbytes
> > filemark 20803 kbytes
> > speed 38376 kps
> > blocksize 128 kbytes
> > }
> >
> > ~290 GB ... faster, and large filemarks.
> >
> > Maybe that drive is somehow failing .. ?
>
> I wasn't sure what LEOM was. I assume it is "Logical End of Media".
>
> Anyway I came across two references that said need for cleaning
> is one reason for getting early EOM.
At this point I would throw in that these drives work on the same
principles as a video tape recorder, and when I walked in the door
in '84 to be the CE at a tv station, hey were using freon TF to clean
tape heads with, and doing it 2-3 times a day on every machine. When
the freon's started to get a bad rap, I switched to paint thinner
alcohol, and made an amazing discovery, suddenly the machines were going
a week before cleanings. But the tape decks used here, are wrapped up in
the mechanics and not readily accessible for such q-tip based cleaning.
I've also observed that tape stored at 40F and 10% humidity is only about
2% as abrasive as tape stored at room temp and humidity. So putting a
tape library in a small closet on an outside wall, with a too small AC
running forever to not only keep it cold but suck all the humidity out
of the air can be very helpfull.
At Nebraska ETV, half the state is in the mountain time zone, so at one
of the tv stations they had 3 of the old 2" Ampex machines, serving as
the 1 hour time delay, and that room was kept at around 55F with a
precipitron equipt HVAC. People, but no smoking, food or drink allowed.
Head life in a normal environment for a 'soft' head on those machines is
around 750 hours. After a while they had a transformer failure and had
to swap heads for a fresh one. It was at that point they read the old
heads spinning hours meter and found it had 9700 hours on it. Sent back
to the rebuilder, he fixed the transformer and sent it back. Put back
in the machine it finally failed at nearly 12,000 hours. Pretty good for
a head with a pro-rated 750 hour warranty. More than demoing the effect
of environment on such stuff.
> I'm wondering also if this could be a case of Amanda tapes being
> labelled with the mode set to LTO-2 capacity. I know you check
> the mode and it shows 44, but Amanda always reads the tape before
> writing. Could this be setting the mode back to 42 because the
> tapes were initially labelled with the mode set incorrectly?
In which case the fix is to read the label block and save it, rewind the
tape but do NOT remove it giving the drive a chance to re-read the tapes
hidden header, use mtx or whatever to set it correctly and rewrite the
label block. The drive will then fix that bad ID in the header before
it writes the label block. If the tape is removed you have to start all
over again because the drive will scan the hidden header and restore the
erronious settings. BTDT, pain in the butt.
> What if you forget about amtapetype and simply use dd to see how
> much random data it will write to tape.
Since the above fix is not a full pass run, but only a few seconds if a
script does it, write the script and do the above first. Much faster.
> Jon
Copyright 2019 by Maurice E. Heskett
Cheers, Gene Heskett
--
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