Date: Sun, 18 Oct 1998 19:24:58 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: gibbs@plutotech.com (Justin T. Gibbs) Cc: tlambert@primenet.com, dkelly@hiwaay.net, freebsd-fs@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG Subject: Re: filesystem safety and SCSI disk write caching Message-ID: <199810181924.MAA19638@usr06.primenet.com> In-Reply-To: <199810162349.RAA11679@pluto.plutotech.com> from "Justin T. Gibbs" at Oct 16, 98 05:42:34 pm
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> >The errors seen are a result of uncommitted data in the drive cache, > >not power spikes and gremlins. The interaction is well understood, > >and on firm footing unrelated to Stephan King novels. > > And why do you think the drive didn't bother to commit the data even > though power was constantly supplied to the drive and only a few, > recent transactions were lost? Most likely because hitting the > reset switch caused a power glitch that reverted the drive to its > power on state. I think it's because the PCI bus POSTed the controller, resulting in a SCSI reset, which lost the uncommitted data. It's a lot easier to believe that than to believe the other. I suppose we should test by making a loadable system call that directly calls the reset code, so as to put the "reset causes a reset reliably, but even though no hardware other than the disk write cache is affected, we believe it's because no one debounced the switch" theory to rest. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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