Hi all,
I'm back and looking for more advice.
Ok, so I got my SCSI stuff running, seemingly smoothly, and decided to try
out RAID again. I started up md0 with 4 drives and 1 spare (actually the
spare was just another partition on one of the base 4 drives but what the
heck). I then make my ext2 and copied in about 2 Gig of stuff and everything
was happy and spinning. Then, I tried to make a backup to my SCSI tape drive
and this also worked fine. Finally I decided to verify the backup and this
died in the middle with oodles of SCSI errors.
Now, instead of trying to figure out specifically what went wrong, I'd like
to ask the SCSI gurus, what is the best way to diagnose SCSI problems. How
do yo know if your cables are too long? Is it a bad idea to set you SCSI
controller to a fast sync speed (e.g., 40 MB/s) when a drive can only handle
5? Under what conditions should I set my controller to asynch for a
particular drive instead of sync? And finally, what is this SCSI stuff so
darn mysterious and difficult? I have a 20 Gig IDE drive that is giving my
about 18MB/s and my fasted SCSI disk only gives me about 9MB/s. What am I
paying so my for SCSI?
Sorry for the slight ranting above. Answers and advice would be
appreciated.
Now, onto RAID. So, I rebooted, set one drive to async (the drive that
seemed to have might have been, maybe, having a few problems, maybe). Now,
so far, the RAID drive seems fine. I created a 2 Gig file and it was happy
with that. I read the file back. Still no problems. Then I did a hdparm
speed test on /dev/md0. Hmm, only 7 MB/s. Why would that be since my fast
single SCSI drives can pump out 9 MB/s. I thought this SCSI 5 stuff was
supposed to INCREASE performance.
Well, at least I enjoy this hacking stuff. Anyone ideas?
--Rainer
