From: Norman Bollinger (norman@STUDENT.CCBC.CC.MD.US)
Date: Mon Sep 08 2003 - 09:35:00 EDT
Back in the 6250 real and later on cartridge days I suffered two failures
that force me to get to the bottom of things and this is what I had to do.
A tape drive has a read while write feature and for the most part we
never see errors because they are fixed on the fly when the read after
write feature can't read the just written block. I had a tape that we
could not read which should never occur unless the drive went bad or the
tape itself went bad but neither was true. The CE left the "turn off
error checking switch" in the no check position and therefore the drive
would never see an error. So I was forced to assure myself that errors
were detected and identified and this is what I had to do. If an error is
detected the software and hardware will erase that potential portion of
the bad media for some distance so you can never be certain that you are
detecting errors unless you actually remove some of the oxide from the
tape for a considerable distance - ie. about 3-4 feet. Then with such a
oxide scratched off tape I was able to demonstrate that errors were
detected and reported. I actually made a reel version and a cartridge
version that I could then write to and see the error and job abort.
It was only after that that I regained my confidence in the tape hardware.
And indeed I only had 2 tapes in my whole 6250 career that could not be read.
That is incredible reliability......
I assume that the 4mm tape has such reliability and if it does not then
we have gone backwards.
So I think you need to discuss this with your harware people to find out
the facts. Or perhaps the 4mm facts will come out on this list and you
can then go from there. I do remember that there was an IBM part number
tape that came with our system that was to be used for diagnostics but
what I don't know is if it had a deliberate bad spot to detect and report
media write errors.
Norman
On Mon, 8 Sep 2003, Tim Muller wrote:
> We are having intermittent tape drive failures during
> the nightly data backup. An errpt is generated each
> time saying probable causes are 'TAPE DRIVE'. The
> drive and all the media has been replaced since this
> began happening, two months ago, but it continues.
> The drive is a 4mm DDS2, the box is a J40 running AIX
> 4.3.2. Any troubleshooting suggestions? TIA.
>
>
> =====
> Tim Muller
> Hamilton Co. Dept. of Job & Family Services
> Cincinnati, OH USA
>
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