Hi,
I had a weird problem with the 2nd SCSI bus of our alpha in the last
couple of days. The 2nd SCSI bus is driven by a simple NCR810 based
controller and has 2 DAT streamers (HP C1533 and HP C1599) and two
CD-ROM drives connected to it.
The problem was that data written to the C1533 streamer was different
when read back from the tape. When I did a compare run with "gtar -d"
some files showed up with "data differs". In the first approach I
blamed the C1533 as the other devices on the bus behaved normal.
Even the C1599 streamer did not show this behaviour.
After numerous tests though, I figured out that the SCSI bus is
the problem! When the C1533 is the only device on the bus, it works
flawlessly. As soon as I connect the other devices (regardless of
whether powered on or off) the C1533 starts getting spurious read
errors.
Now: The most funny thing is: These read errors are silent, meaning
that you won't notice them unless you can compare the data with the
original data. There are no errors logged in any of the log files.
I have always thought that the SCSI bus has parity and would catch
errors like these?
So my question: Can anyone provide more information about SCSI parity
and whether or not DU would log them in syslog/binary.errlog. How
can SCSI parity be enabled/disabled.
Thanks a lot -- Tom
BTW: The cheap NCR810 has passive on-board termination. I was told that
there is a special active SCSI terminator from Digital which can be
plugged on the internal SCSI connector of the controller which replaces
the passive termination and thus improves the bus quality. Can anyone
confirm this?
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Received on Thu Apr 09 1998 - 17:16:05 NZST