Date: Sun, 7 Jun 2009 09:01:34 +0200 (CEST) From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> To: Freddie Cash <fjwcash@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Request for opinions - gvinum or ccd? Message-ID: <alpine.BSF.2.00.0906070858210.97807@wojtek.tensor.gdynia.pl> In-Reply-To: <b269bc570906061316g37290b5q910da0d3ec266c98@mail.gmail.com> References: <20090530175239.GA25604@logik.internal.network> <20090530144354.2255f722@bhuda.mired.org> <20090530191840.GA68514@logik.internal.network> <20090530162744.5d77e9d1@bhuda.mired.org> <A5BB2D2B836A4438B1B7BD8420FCC6A3@uk.tiscali.intl> <h0ehhv$sic$1@ger.gmane.org> <b269bc570906061316g37290b5q910da0d3ec266c98@mail.gmail.com>
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>> (very roughly, in the non-sequential access case) expected to deliver >> performance of four drives in a RAID0 array? > > According to all the Sun documentation, the I/O throughput of a raidz > configuration is equal to that of a single drive. exactly what i say. it's like RAID3. Not RAID5 which have close to n times single drive throughput on read and rougly n/4 on writes. > We remade the pool using 3x 8-drive raidz2 vdevs, and performance has > been great (400 MBytes/s write, almost 3 GBytes/s sequential read, 800 why write performance is so slow? in Sun theory it should have the same speed as reads. I would say that it should be even better a bit - filesystem get data first in cache and can plan ahead. > MBytes/s random read). random read on how big chunks? Are you sure you get 3GB/s on read? it would mean each drive must be able to do 140MB/s What disks do you use?
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