Date: Sat, 13 Apr 2002 13:22:40 -0700 From: David Schultz <dschultz@uclink.Berkeley.EDU> To: Gregory Keefe <keefeg@keefeg.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Softupdates Message-ID: <20020413132240.A22260@HAL9000.wox.org> In-Reply-To: <002301c1e31e$1dbe2850$9865fea9@GPC>; from keefeg@keefeg.com on Sat, Apr 13, 2002 at 03:05:02PM -0400 References: <002301c1e31e$1dbe2850$9865fea9@GPC>
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Thus spake Gregory Keefe <keefeg@keefeg.com>: > FreeBSD Claim: > http://www.freebsd.org/features.html > Soft Updates allows improved file system performance without sacrificing > safety and reliability > > A Unix Expert's Claim: > http://cr.yp.to/qmail/faq/reliability.html > ``Do not use async or softupdates filesystems. If you do, and if your system > crashes at the wrong moment, you will lose [data].'' > > http://cr.yp.to/daemontools/multilog.html > ``Beware that NFS, async filesystems, and softupdates filesystems may > discard files that were not safely written to disk before an outage.'' DJB's statements are correct, but they do not tell the whole story. Async mounts, the default in Linux, are fast but dangerous because a crash can potentially cause irreparable filesystem corruption. Softupdates, the default in FreeBSD, does not corrupt your filesystem in the event of a crash and is about as fast as async. This is what the first quote means by `safe'. However, under softupdates, writes can be delayed up to 30 seconds; after a crash, your filesystem is fine, but you could lose any mail you received in the last 30 seconds. If this is not acceptable, you can use a synchronous mount, but it will be horribly slow! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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