Date: Sun, 29 Oct 2006 23:05:32 -0800 (PST) From: "R. B. Riddick" <arne_woerner@yahoo.com> To: performance@freebsd.org Subject: Re: gvinum raid5 performance seems slow Message-ID: <20061030070532.5495.qmail@web30309.mail.mud.yahoo.com> In-Reply-To: <20061030051913.GG1052@wantadilla.lemis.com>
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--- Greg 'groggy' Lehey <grog@FreeBSD.org> wrote: > "Sufficiently large data blocks" equates to several megabytes. > Currently MAXPHYS, the largest transfer request that would get to the > bio layer, is 131072 bytes. This would imply a stripe size of not > more than 32 kB for a five disk array, which is unrealistically small. > > I did consider this optimization, but it would only work if Vinum were > first to buffer multiple requests, and there are all sorts of > reliability issues there. For example, you'd have to lie about the > first few requests that were only buffered and not actually sent out > to disk. Possibly it should be done anyway. > I did it that way in my graid5 class: http://home.tiscali.de/cmdr_faako/geom_raid5.tbz The source might look somehow incomprehensible, but it seems to be quite stable (on amd64 and i386)... I tried to benchmark with a 3 disk array: Single disk: 30MB/sec write speed graid5 device: 20MB/sec write speed I would be interested in other benchmarks about it. -Arne ____________________________________________________________________________________ Get your email and see which of your friends are online - Right on the New Yahoo.com (http://www.yahoo.com/preview)
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