Date: Thu, 19 Jul 2007 20:33:59 +0100 (BST) From: "Mark Powell" <M.S.Powell@salford.ac.uk> To: Doug Rabson <dfr@rabson.org> Cc: freebsd-fs@freebsd.org Subject: Re: ZfS & GEOM with many odd drive sizes Message-ID: <20070719203134.B4923@rust.salford.ac.uk> In-Reply-To: <200707192027.44025.dfr@rabson.org> References: <20070719102302.R1534@rust.salford.ac.uk> <20070719135510.GE1194@garage.freebsd.pl> <20070719181313.G4923@rust.salford.ac.uk> <200707192027.44025.dfr@rabson.org>
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On Thu, 19 Jul 2007, Doug Rabson wrote: > On Thursday 19 July 2007, Mark Powell wrote: >> Should I expect much greater CPU usage with ZFS? >> I previously had a geom raid5 array which barely broke a sweat on >> benchmarks i.e simple large dd read and writes. With ZFS on the same >> hardware I notice 50-60% system CPU usage is usual during such tests. >> Before the network was a bottleneck, but now it's the zfs array. I >> expected it would have to do a bit more 'thinking', but is such a >> dramatic increase normal? >> >> Many thanks again. > > ZFS does a checksum on every block it reads from the disk which may be > your problem. In normal usage, this isn't a big deal due because many > reads get data from the cache. I've turned off checksums, but still my machine is struggling. I think my Athlon XP is a little old for all this work :( Any other tips for speeding zfs up? Cheers. -- Mark Powell - UNIX System Administrator - The University of Salford Information Services Division, Clifford Whitworth Building, Salford University, Manchester, M5 4WT, UK. Tel: +44 161 295 4837 Fax: +44 161 295 5888 www.pgp.com for PGP key
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