Date: Mon, 30 Aug 1999 19:12:15 +1000 From: Stephen McKay <syssgm@detir.qld.gov.au> To: freebsd-current@freebsd.org, freebsd-scsi@freebsd.org Cc: syssgm@detir.qld.gov.au Subject: SCSI surprise! (was: Softupdates reliability?) Message-ID: <199908300912.TAA00547@nymph.detir.qld.gov.au>
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[I'm trying my first crosspost experiment here. Please follow up to -scsi.] A week ago I posted my strange crash and subsequent doubts about the proper functioning of softupdates. This is more of the story. I examined the lost+found directory more closely and of the few files that I traced, they were all temporary files or newly created directories (ports actually) created in the CTM update process. So, maybe I didn't really lose anything. Maybe fsck just doesn't recognise one of the safe-but-crashed modes you get when using softupdates. But unfortunately, I needed a CVS tree urgently and restored a backup. To make up for this, I promise to do serious destruction testing of softupdates soon. But, I had another crash almost as soon as I started using the machine again. Again, the Exabyte was being used (but only rewinding at the time), but the obvious trigger this time was intense disk activity (from "rm"). The active file system was not using softupdates, and had a number of fsck -p correctable errors on reboot. Conclusions: 1) The Exabyte was not to blame for the crash 2) The crash wasn't a "scribble junk" crash (first one probably wasn't either) 3) Regular mounts are still safer than softupdates I took the lid off anyway hoping to find anything at all weird and noticed something I had forgotten. I was using a Seagate ST51080N 1GB disk earlier for some experimenting and had disconnected the POWER, but not the SCSI CABLE. (It's a really noisy drive!) When I also unplugged the SCSI cable, all crashes stopped. I've now used the machine intensively for several days (copying over 20GB of small and big files, and read and written several tapes) without incident. Conclusions: 4) My stepping of K6-2/300 is just fine 5) My Exabyte really is ok :-) 6) It is NOT safe to have a powered down SCSI device attached to a SCSI chain 7) The world really is a wonderful place ;-) So, apart from being happy at having stable hardware again, I am intensely curious about this. Why is a powered down SCSI device so nasty? For example, the first crash locked up my SCSI card so that reset didn't fix it, and the second crash hung one of my disks so that it had to be powered down to even be recognised! Is there a standard for this stuff? Stephen. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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