Date: Tue, 19 Oct 2004 13:39:48 +0200 From: fandino <fandino@ng.fadesa.es> To: freebsd-current@freebsd.org Subject: Re: FreeBSD 5.3b7and poor ata performance Message-ID: <4174FD04.8040000@ng.fadesa.es> In-Reply-To: <417406E3.9010706@DeepCore.dk> References: <20041015190638.C5A0E5D04@ptavv.es.net> <41715E7F.7060509@ng.fadesa.es> <20041018100045.f8koww0skcco0woo@www.sweetdreamsracing.biz> <4173D66F.6010200@DeepCore.dk> <4173F2E9.7010407@ng.fadesa.es> <417406E3.9010706@DeepCore.dk>
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S=F8ren Schmidt wrote: >> # dd if=3D/dev/ad4 of=3D/dev/null bs=3D1024k count=3D1024 >> 1024+0 records in >> 1024+0 records out >> 1073741824 bytes transferred in 31.090536 secs (34535970 bytes/sec) > > etc, and I get this: > 1073741824 bytes transferred in 18.488903 secs (58074934 bytes/sec) > 1073741824 bytes transferred in 14.956484 secs (71791059 bytes/sec) >> I'd like to know wich is you opinion about this. > > If you run a stock generic kernel with the debug (WITNESS etc) taken ou= t=20 > you should see the same raw performance as I do. I redid all tests with __RC1__ and performance is as bad as before. > Now, raw performance is one thing, filesystem I/O something entirely I think the problem is with raw performace, just see this example with a test raid0. Each disk by separate has a throughput of 26000 K/sec,= with /dev/stripe/test they have a throughput of 15000 K/sec each (raid0 throughput 30000 K/sec) and with four disks 7500 K/sec each (30000 K/sec again). # dd if=3D/dev/stripe/test of=3D/dev/null bs=3D1024k count=3D1024 1024+0 records in 1024+0 records out 1073741824 bytes transferred in 30.072215 secs (35705445 bytes/sec) There is a constant limit of 30000 K/sec independent of the number of disks used. simply it doesn't makes any sense. With two disk I'd must have approx. 26K+26K=3D52 M/sec and with four 26K+26K+26K+26K=3D104 M/sec Other systems like OpenBSD had a good throughput 55000K/sec by disk I send you in another email with all info that you need. Regards,
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