Date: Thu, 28 Jan 2010 15:43:33 +0200 From: Urmas Lett <urmas.lett@eenet.ee> To: freebsd-fs@freebsd.org Subject: Reading from ZFS mirror 2x slower than expected? Message-ID: <4B619485.8080106@eenet.ee>
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While reading from simple zfs mirror 'dd if=zfs.test of=/dev/null bs=512k' systat -vm shows individual disks only 50% busy: Disks ad4 ad8 ad10 KB/t 0.00 128 128 tps 0 273 285 MB/s 0.00 34.15 35.64 %busy 0 51 48 reading from one disk 'dd if=/dev/ad8 of=/dev/null bs=512k' is 2x faster: Disks ad4 ad8 ad10 KB/t 0.00 128 0.00 tps 0 769 0 MB/s 0.00 96.09 0.00 %busy 0 97 0 and even writing to the same mirror is 2x faster: Disks ad4 ad8 ad10 KB/t 0.00 128 128 tps 0 654 707 MB/s 0.00 81.76 88.36 %busy 0 100 100 -- Urmas Lett Tel: +(372) 7 302 110 Fax: +(372) 7 302 111 E-Mail: urmas.lett@eenet.ee
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