Date: Sat, 23 Mar 2002 19:09:43 -0500 (EST) From: Robert Watson <rwatson@freebsd.org> To: John Hanley <jh_@yahoo.com> Cc: Willie Viljoen <will@laserfence.net>, freebsd-fs@freebsd.org, re@freebsd.org Subject: Re: Soft update instability with heavy IO and offboard IDE controller Message-ID: <Pine.NEB.3.96L.1020323190730.47668K-100000@fledge.watson.org> In-Reply-To: <20020323235545.32054.qmail@web10105.mail.yahoo.com>
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On Sat, 23 Mar 2002, John Hanley wrote: > > turn off write caching at boot time in > > /boot/loader.conf by adding the line hw.ata.wc=0 > > Surely a default install should result in write caching disabled, right? > Since any new filesystems will default to using soft update. We turned it off by default in 4.4-RELEASE, I believe, and got utterly pounded in the benchmarks, magazine reviews, etc, and turned it back on for later RELENG_4 releases. On 5.0-CURRENT, it's off again by default due to the assumptions concerning background fsck, which is on by default. At some point, we need to have that whole discussion again. Basically, vendors ship hardware that don't conform to standards specifications, and consistency guarantees are thrown out the window if you use the default settings. If you disable write caching, you will see a very high performance hit on most modern disks. I suppose we need to think about this for DP1 also. Robert N M Watson FreeBSD Core Team, TrustedBSD Project robert@fledge.watson.org NAI Labs, Safeport Network Services To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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