Date: Wed, 23 Jul 2008 00:08:40 +0200 From: Miroslav Lachman <000.fbsd@quip.cz> To: Matt Simerson <matt@corp.spry.com> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS hang issue and prefetch_disable Message-ID: <48865A68.1010504@quip.cz> In-Reply-To: <5E8D64DE-EC9B-4B11-BCB4-17BA63650BB7@corp.spry.com> References: <5E8D64DE-EC9B-4B11-BCB4-17BA63650BB7@corp.spry.com>
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Matt Simerson wrote: > Symptoms > > Deadlocks under heavy IO load on the ZFS file system with > prefetch_disable=0. Setting vfs.zfs.prefetch_disable=1 results in a > stable system. [...] > With vfs.zfs.prefetch_disable=1, a hang will occur within a few hours > (no more than a day). If I keep the i/o load (measured via iostat) down > to a low level (< 200 iops) then I still get hangs but less frequently > (1-6 days). The only way I have found to prevent the hangs is by > setting vfs.zfs.prefetch_disable=1. "With vfs.zfs.prefetch_disable=1, a hang will occur within...", did you realy mean prefetch_disable=1 in this sentence? Your whole e-mail seems that prefetch_disable=1 is good workaround, so I expect you have prefetch_disable=0 previously which causes hangs... Miroslav Lachman
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