Date: Wed, 16 Mar 2011 14:48:35 +0100 From: Lorenzo Perone <lopez.on.the.lists@yellowspace.net> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: gmirror performance Message-ID: <4D80BFB3.20706@yellowspace.net> In-Reply-To: <ilq8pl$qgf$1@dough.gmane.org> References: <4D7F7E33.7050103@yellowspace.net> <ilq8pl$qgf$1@dough.gmane.org>
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On 16.03.11 13:00, Ivan Voras wrote: > On 15/03/2011 15:56, Lorenzo Perone wrote: ... >> I'd expect read performance to be noticeably higher than write >> performance. Why is it not the case? Wrong expectation? :/ > Maybe. You can't expect that RAID-1 will have as good performance as > RAID-0 but you might achieve better performance for sequential reads > with long buffers. Try setting the vfs.read_max sysctl to 128 and see if > it helps you. It *does* help! Thanx a great lot! I knew I it was a PEBKAC :) sysctl vfs.read_max=128 configure -b load mirr0 just gave me 70MB/s more when reading (256640376 bytes/sec) :) > (you might want to leave the gmirror algorithm to the >> default "load" and increase the stripe size to something sane, like 16k). If You meant gmirror configure -s 16384 mirr0: this didn't change anything for -b load, as expected, but it did change a little for -b split. To sum up some results, fwimc: test case: umount /mnt && mount /dev/mirror/mirr0p4 /mnt && \ dd if=/mnt/2gigfile.dat bs=1m of=/dev/null * with default vfs.read_max=8 -b split -s 2048: 173875942 bytes/sec -b load: 195143412 bytes/sec * with vfs.read_max=128 -b split -s 2048: 191024137 bytes/sec -b load: 258329216 bytes/sec Big Thanx and Regards, Lorenzo
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