Date: Thu, 28 Jan 2010 13:54:14 -0600 (CST) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Urmas Lett <urmas.lett@eenet.ee> Cc: freebsd-fs@freebsd.org Subject: Re: Reading from ZFS mirror 2x slower than expected? Message-ID: <alpine.GSO.2.01.1001281350210.17824@freddy.simplesystems.org> In-Reply-To: <4B619485.8080106@eenet.ee> References: <4B619485.8080106@eenet.ee>
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On Thu, 28 Jan 2010, Urmas Lett wrote: > While reading from simple zfs mirror 'dd if=zfs.test of=/dev/null bs=512k' > systat -vm shows individual disks only 50% busy: How big is the file 'zfs.test'? How was it created? If it was created from /dev/zero then its content is bogus. You need to test with non-zero data. It may be that zfs's prefetch is not working adequately. With perfect prefetch, the read rate should be doubled. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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