Date: Tue, 03 Mar 1998 14:06:52 -0800 From: Julian Elischer <julian@whistle.com> To: "Alok K. Dhir" <adhir@worldbank.org> Cc: roberto@keltia.freenix.fr, freebsd-current@FreeBSD.ORG Subject: Re: Panic with CURRENT & softupdates-240298 Message-ID: <34FC7EFC.237C228A@whistle.com> References: <Pine.NEB.3.96.980303164538.6994B-100000@shadow.worldbank.org>
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Alok K. Dhir wrote: > > Mind explaining what soft-updates does? > Soft Updates is a method of keeping track of teh dependencies within the metadata of a filesystem, so that you can ensure that at every stage, the on-disk image is consistent. It includes such techniques as temporarily backing out certain changes during disk writes, and queuing up a lot of extra information. This seems a lot of work, however the gain is that: 1/ after a crash fsck is not really required. (except to recover blocks marked in use but really freed in the last few seconds of running before the crash) 2/ The writes are ALL (unles you do a fsync()) done async, 3/ The dependencies automatically notice things like: "I'm about to write a file but it's already been deleted" and cancels the operation. 4/ metadata operations such as deletion are grouped up and done in bulk which is WAY faster. (that's just a quick start) julian To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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