Date: Mon, 2 May 2005 15:19:10 -0700 (PDT) From: Arne "Wörner" <arne_woerner@yahoo.com> To: Steven Hartland <killing@multiplay.co.uk>, Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Robert Watson <rwatson@freebsd.org> Subject: Re: Very low disk performance on 5.x Message-ID: <20050502221910.36685.qmail@web41205.mail.yahoo.com> In-Reply-To: <00fe01c54f61$df220d60$b3db87d4@multiplay.co.uk>
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--- Steven Hartland <killing@multiplay.co.uk> wrote: > ----- Original Message ----- > From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> > > On -current and 5.4 you don't have to make partitions if you > > intend to use the entire disk (and provided you don't want > > to boot from it). You can simply: > > > > newfs /dev/da0 > > mount /dev/da0 /where_ever > > /dev/da0: 1526216.3MB (3125691008 sectors) block size 16384, > fragment size 2048 > using 8306 cylinder groups of 183.77MB, 11761 blks, 23552 > inodes. > mount /dev/da0 /mnt > > dd if=/dev/zero of=/mnt/testfile bs=64k count=100000 > 100000+0 records in > 100000+0 records out > 6553600000 bytes transferred in 44.424588 secs (147521908 > bytes/sec) > > /usr/bin/time -h dd of=/dev/null if=/mnt/testfile bs=64k > count=100000 > 100000+0 records in > 100000+0 records out > 6553600000 bytes transferred in 48.150473 secs (136106658 > bytes/sec) > 48.27s real 0.01s user 12.33s > sys > > /usr/bin/time -h cat /mnt/testfile > /dev/null > 48.12s real 0.26s user 14.92s > sys > > Raw read: > /usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=64k count=100000 > > 100000+0 records in > 100000+0 records out > 6553600000 bytes transferred in 32.028544 secs (204617482 > bytes/sec) > 32.02s real 0.02s user 2.73s > sys > > /usr/bin/time -h dd of=/dev/null if=/dev/da0 bs=1m count=6000 > 6000+0 records in > 6000+0 records out > 6291456000 bytes transferred in 31.518195 secs (199613460 > bytes/sec) > 31.51s real 0.00s user 1.87s > sys > > > One thing you could try is to use a larger block/fragment size > > on your filesystem. Try: > > > > newfs -b 32768 -f 4096 /dev/da0 > /dev/da0: 1526216.3MB (3125691008 sectors) block size 32768, > fragment size 4096 > using 2063 cylinder groups of 740.00MB, 23680 blks, > 47360 inodes. > > /usr/bin/time -h dd if=/dev/zero of=/mnt/testfile bs=64k > count=100000 > 100000+0 records in > 100000+0 records out > 6553600000 bytes transferred in 35.237328 secs (185984590 > bytes/sec) > 35.34s real 0.07s user 28.81s > sys > > /usr/bin/time -h dd of=/dev/null if=/mnt/testfile bs=64k > count=100000 > 100000+0 records in > 100000+0 records out > 6553600000 bytes transferred in 39.154845 secs (167376477 > bytes/sec) > 39.16s real 0.01s user 14.33s > sys > > Slower than the default :( > Why? It looks like the 32k-bs-fs terminates 20% earlier than the 16k-bs-fs. Furthermore I would like to re-interpret my analysis about my hard disc /dev/ad0: It looks like, I damaged the write cache somehow... atacontrol's output is not consistent in this point (it changes from reboot to reboot, while the write rate is always 5 times lower than the read rate), while hw.ata.wc is always 1. So I just see, that there is some overhead. Example: my /dev/ad1: 92MB/sec theoretical maximum (data transfer rate from the medium (disc) to device's buffer) 60MB/sec if I read bs=128k 40MB/sec if I read from a ufs+s with std bs (16kB?) -Arne __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
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