Date: Wed, 23 Dec 2009 15:03:59 -0600 (CST) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Solon Lutz <solon@pyro.de> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS RaidZ2 with 24 drives? Message-ID: <alpine.GSO.2.01.0912231459010.1586@freddy.simplesystems.org> In-Reply-To: <1696529130.20091223212612@pyro.de> References: <568624531.20091215163420@pyro.de> <42952D86-6B4D-49A3-8E4F-7A1A53A954C2@spry.com> <957649379.20091216005253@pyro.de> <26F8D203-A923-47D3-9935-BE4BC6DA09B7@corp.spry.com> <1696529130.20091223212612@pyro.de>
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On Wed, 23 Dec 2009, Solon Lutz wrote: > I opted for two 12-disc raidz2. > Reasons were: Space is more important than performance. > > But performance is very poor - have a look at the iostats - sometimes nothing really seems > to happen for up to ten seconds, or very little data gets written. Might this be a problem > of the amd64 system having only 4GB of RAM? Any tuneable sysctls? Enabling prefetch didn't help...: The most likely cause is that several of your disks are not performing properly. Perhaps a disk is performing error recovery, or there is a bad cable, or maybe even too much chassis vibration. It only takes one pokey disk in a vdev to slow down the whole vdev. Using 'iostat -x 10' while your pool is under continous I/O load may help find the pokey disks. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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