Date: Tue, 09 Mar 2004 20:39:49 +0100 From: Poul-Henning Kamp <phk@phk.freebsd.dk> To: current@freebsd.org Subject: MD(4)/vnode hangs resolved (?) Message-ID: <34954.1078861189@critter.freebsd.dk>
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Those of you who have experienced that md(4) backed by vnodes hang your systems, please try this patch: http://phk.freebsd.dk/patch/md.patch It changes so that vnode backed md(4) devices use IO_SYNC by default (can be overridden with "async" option to mdconfig(8)). This solves the case where the system get stuck in "wdrain" because a md(4)/vnode device is relatively large compared to the buffer cache. Another benefit is that this makes the md(4)/vnode devices behave like a proper disk with no write-caching. Performance sucks though. But slow performance is still better than hung systems. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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