Date: Sat, 4 Aug 2012 14:27:58 +0100 From: Steve O'Hara-Smith <steve@sohara.org> To: freebsd-questions@freebsd.org Subject: ZFS bonnie puzzlement Message-ID: <20120804142758.0126fded.steve@sohara.org>
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Hi, I've been looking at the performance of my new NAS box - built using a Jetway JNF99FL-525 with 4GB of 1066 DDR3 and a pair of 2TB Samsung F4 drives in a mirror. It all works but the performance reports are puzzling Running bonnie -s 8192 - reports character and block write times of around 66MB/s which is consistent with what zpool iostat -v and systat -v are showing me. Read performance OTOH is strange, zpool and systat both reporting consistently an aggregated read speed of around 120MB/s during the block read tests (which seems a bit slow for the drives - and indeed systat reports the drives at less than 50% utilisation) but bonnie is only reporting 35MB/s, I see similar discrepancies with simple dd block reads to /dev/null, in which case my stopwatch agrees with dd. I made some more bonnie tests on the boot SSD - there everything is as expected systat and bonnie agree and the disc gets pushed to 90-100% utilisation with write speeds over 100MB/s and read speeds over 250MB/s. Also a dd of the raw drive (read only of course) runs the drives up to around 130MB/s easily - dd and systat agree about the speed. First up can anyone explain the discrepancy between bonnie and zpool/systat for the XFS pool ? Secondly can anyone suggest a reason that I can't seem to get the drives above 50% reported utilisation on reads ? -- Steve O'Hara-Smith | Directable Mirror Arrays C:>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
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