Date: Tue, 07 Dec 1999 08:04:27 -0700 From: "Justin T. Gibbs" <gibbs@FreeBSD.org> To: Mike Smith <msmith@FreeBSD.org> Cc: Julian Elischer <julian@whistle.com>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern kern_shutdown.c Message-ID: <199912071504.IAA00354@caspian.plutotech.com> In-Reply-To: Your message of "Mon, 06 Dec 1999 22:17:09 PST." <199912070617.WAA00550@mass.cdrom.com>
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>> Softupdates is pointless without this because Soft Updates cannot >> guarantee the state of the filesystem to be sane unless the disk does not >> lie about whether it has written to the disk. > >This is kinda immaterial except at completion boundaries. Whether you >wait for the disk to flush its cache, or mandate that it flushes >immediately after each transaction, the net result is the same. > >> Soft updates also makes all >> the writes async, so who cares.. :-) > >Anyone who cares about the drive's ability to sort outstanding cache line >writes for optimal throughput. Remember that softupdates doesn't care if the drive does write behind so long as it only acknowledges that the write has completed once the drive can guarantee it will hit the platters. Usually this means that it has been written, but it may mean that the head is on cylinder and that the data can be written (barring a media failure) even if power is lost. You should get this behavior if you disable write caching on the disk, and with tagged queuing, the drives firmware should still have plenty of information to sort how it clears its write buffer. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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