Date: Fri, 05 Mar 1999 05:26:31 +1000 From: Greg Black <gjb@comkey.com.au> To: Roelof Osinga <roelof@eboa.com> Cc: Chris Tubutis <chris@tci.com>, freebsd-questions@FreeBSD.ORG Subject: Re: Have crashed, won't travel Message-ID: <19990304192631.12019.qmail@alpha.comkey.com.au> In-Reply-To: <36DEBBC8.6B5B5EDD@eboa.com> of Thu, 04 Mar 1999 17:58:48 %2B0100 References: <36DCB59E.F16D5539@eboa.com> <19990303195632.B441@lemis.com> <36DDBFEB.86D89D20@eboa.com> <19990304095813.I441@lemis.com> <36DDEFFD.A4DB4978@eboa.com> <19990304130126.B441@lemis.com> <36DE0352.E99BCB70@eboa.com> <36DEA481.7ABA8AF3@tci.com> <36DEBBC8.6B5B5EDD@eboa.com>
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It's rare (but still possible) for modern Unix systems to suffer a lot of damage, even in the face of power failures. A normal consequence of a power failure will be a few minor problems that fsck can quite safely correct. If the system is doing heavy disk activity at the instant of the power failure, there might be a bit more damage, although I've never seen more than 20 files end up in lost+found directories in twenty years with Unix systems. For this reason, I never bothered with a UPS for my home Unix system(s) because my time to recover was typically of the order of ten minutes and power failures happened about once every 18 to 24 months where I lived. But when I moved to my present location (a bit over 3 years ago), I found that I could no longer get any work done because the power here goes out for a second or two four or five times a day. Not all the computers crashed on each power failure, but it was no way to get any work done. So I installed some UPSes and I've had no dramas -- until yesterday. We had a sudden storm. A nearby electricity sub-station exploded spectacularly; the power surged high, the UPSes clipped it; it went off, the UPSes went to battery; I ran around the house shutting windows to keep out the torrential rain and wind; the power came back, went off, came back, went off, came back at around 90 volts (we run 240 nominal here) and stayed there for an hour. The it went off and returned normally and I went to check my computers. I don't know if the shenanigans with the power confused the UPSes into giving dodgy output to the monitoring software or if there is a bug in the software, but the usual shutdowns that should have been run when the power had been off for 3 minutes did not run on two of the three UPSes, so the five machines attached to them all had the power yanked without warning. I was a bit apprehensive, since those machines were active at the time and between them had about 830,000 files -- plenty of scope for wasting time. I brought each machine up by hand, ran fsck -n manually, studied the output, and was delighted to see that there was nothing to be fixed of any significance. BTW, those five machines all run FreeBSD-2.2.8-Release. Now all I have to do is figure out how to simulate the storm so I can see if there is a bug in the UPS monitoring software or if it's a problem with the UPSes :-) -- Greg Black <gjb@acm.org> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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