Date: Thu, 13 Nov 2003 15:15:10 +0100 From: Andreas Braukmann <braukmann@tse-online.de> To: Martin Blapp <mb@imp.ch> Cc: Allen Briggs <briggs@wasabisystems.com> Subject: Re: Very bad FreeBSD SCSI RAID5 write speed performance Message-ID: <2147483647.1068736510@[192.168.111.140]> In-Reply-To: <20031113142735.S13503@cvs.imp.ch> References: <20031112172306.J4572@pooker.samsco.home> <20031113084355.P13503@cvs.imp.ch> <20031113132327.GF13029@canolog.ninthwonder.com> <20031113142735.S13503@cvs.imp.ch>
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--On Donnerstag, 13. November 2003 14:29 Uhr +0100 Martin Blapp <mb@imp.ch> wrote: >> On Thu, Nov 13, 2003 at 06:38:53AM -0500, Gary Stanley wrote: >> > root@64:[/tmp/blah]>dd if=/dev/zero of=/tmp/blah/blah >> > 89472+0 records in >> > 89471+0 records out >> > 45809152 bytes transferred in 8.546312 secs (5360108 bytes/sec) ServerWorks Chipset, PIII 1 GHz, Adaptec 5400S, Raid-5 over four spindles (Fujitsu U160, 10kUPM disks, write cache off) on one channel, -current from end of september: roach:[/home/ab] # dd if=/dev/zero of=./test bs=128k count=20000 20000+0 records in 20000+0 records out 2621440000 bytes transferred in 66.062844 secs (39681004 bytes/sec) Another system: Tyan K8S, Adaptec 2200S, RAID-5 over five spindles (Fujitsu U320, 10kUPM disks, write-cache off) across both channels, -current from end of september (i386): opti# dd if=/dev/zero of=./test bs=128k count=20000 20000+0 records in 20000+0 records out 2621440000 bytes transferred in 57.648042 secs (45473184 bytes/sec) > Exactly what we get here: ~ 6MB per second with RAID5 and the IPS > driver. The Adaptec 3200s is similar. I'll update the Opteron box to a recent kernel and will check again. > A single disk has writes to the 53MB to the raw slice. I don't > know why 5 equal disks on 2 busses are that slow. What about the write cache settings on the disks and on the raid-controllers? Both of my controllers are equipped with battery backup modules for the controller cache and are set to "write behind caching". Turning off the controller's write cache leads to raid-5 write performance less than 10 MByte/s. -Andreas
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