Date: Sat, 25 Jan 2003 13:38:59 -0800 From: David Schultz <dschultz@uclink.Berkeley.EDU> To: Nate Lawson <nate@root.org> Cc: current@FreeBSD.ORG Subject: Re: I've just had a massive file system crash Message-ID: <20030125213859.GB6339@HAL9000.homeunix.com> In-Reply-To: <Pine.BSF.4.21.0301251048090.79988-100000@root.org> References: <20030125070352.GA933@HAL9000.homeunix.com> <Pine.BSF.4.21.0301251048090.79988-100000@root.org>
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Thus spake Nate Lawson <nate@root.org>: > On Fri, 24 Jan 2003, David Schultz wrote: > > Thus spake Greg Lehey <grog@FreeBSD.ORG>: > > > I've been thinking about what happened, and I have a possibility: the > > > session before shutdown included a lot of writing to that file system, > > > and I did a shutdown -p. It's possible that the shutdown powered off > > > the system before the disk had flushed its cache. For the moment I'm > > > avoiding shutdown -p, but when I get home I'll try to provoke it > > > again. > > > > FreeBSD's ``fix'' for this problem is the same as Windows 98's. > > Specifically, there is a 5-second delay (tuneable: > > kern.shutdown.poweroff_delay) after all buffers are flushed but > > before the power is cut. Maybe we ought to be sending FLUSH > > CACHE commands to all drives and waiting for them to finish. > > da(4) does a SYNC CACHE (see daclose() and dashutdown()). Good. I was referring to IDE in this case, because I assume that's what Greg's laptop uses. The ATA driver flushes the cache when the device is closed, but I don't think that happens during shutdown. It probably needs to register a shutdown hook like the SCSI driver. Also, the driver is a bit optimistic about how long the flush will take; it times out after 5 seconds, whereas the ATA spec says a flush can take up to 30 seconds. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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