Cabling / termination question: DDS3 drive with errors
Palmisano
I am not very much into SCSI, but maybe an expert here can easily give
an answer to the following:
HARDWARE/SOFTWARE
I have a RedHat Linux 8.0 PC with a new Tek DC395-UW SCSI2 host
adapter. Also a new HP DD3 streamer (C1537A), which is SE SCSI2 (and
NEW tapes).
PROBLEM
The streamer is recognised by Linux, I can rewind and eject, I can
write and read data, but when I write and read back a file, the
read-back file is not equal to the original. I get something like
this:
$ dd if=bigfile_org of=/dev/st0
$ dd if=/dev/st0 of=bigfile_out
$ cmp bigfile_org bigfile_out
bigfile_org and bigfile_out differ
byte 166 line 1
I believe the writing goes wrong, because the erroneous byte is always
the same when I read the tape again. When I do the whole sequence
again, the erroneous byte is somewhere else.
I also wrote a short c-program to write a series of 512-byte blocks
with a pattern en then read back the tape in 512-byte blocks. Some
blocks are then correct but of some blocks the last byte changes into
0xB4 (irrespective of the write pattern: e.g. 0xAA, 0xFF).
The sequence numbers of the erroneous blocks vary when I redo the
test.
CABLING
I suspect that there may be something wrong with termination and/or
cabling.
1. Can that be the case? As said: I can eject, rewind and some I/O is
OK.
2. I find the cabling suspect: I have a ribbon cable with 3 50-pin
connectors (everything is built-in. One end of the cable is in the
host adapter, the middle connector is in the tape and the other hand
is hanging loose. I do not have any terminators
The tape driver has a switch for TRM power (but the manual says: is
not used in HP workstation configuration...).
I don't have a good feeling about not having a terminator connected,
but I don't know if I need that (in the old days I remember the clumsy
terminator blocks, but I believe that many devices have built in
terminators nowadays?).
I hope this is enough info. Thanks for your patience reading this and
for any suggestions!
Remco (The Netherlands)