Date: Sun, 24 Aug 2003 22:18:05 -0500 From: "Chris Newman" <canman@ev1.net> To: "'Erik Trulsson'" <ertr1013@student.uu.se> Cc: freebsd-questions@FreeBSD.ORG Subject: RE: hard disk performance issue Message-ID: <000001c36ab7$8017aae0$0300a8c0@owl> In-Reply-To: <20030825003158.GA72370@falcon.midgard.homeip.net>
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Hmm... when I do what you suggest, here's what I get... tigger# dd if=/dev/ad8s1d of=/dev/null bs=64k count=100 100+0 records in 100+0 records out 6553600 bytes transferred in 0.147501 secs (44430888 bytes/sec) tigger# dd if=/dev/ad8s1d of=/dev/null bs=100k count=100 100+0 records in 100+0 records out 10240000 bytes transferred in 0.230168 secs (44489246 bytes/sec) tigger# dd if=/dev/ad8s1d of=/dev/null bs=200k count=100 100+0 records in 100+0 records out 20480000 bytes transferred in 0.429506 secs (47682693 bytes/sec) ~47MB ? huge difference I'm still not sure at this point what the best way is to evaluate whether I'm getting my money's worth out of this disk/controller. How do I do a good benchmark of the speed? Thanks, cn -----Original Message----- From: Erik Trulsson [mailto:ertr1013@student.uu.se] Sent: Sunday, August 24, 2003 7:32 PM To: Chris Newman Cc: freebsd-questions@FreeBSD.ORG Subject: Re: hard disk performance issue On Sun, Aug 24, 2003 at 06:16:11PM -0500, Chris Newman wrote: > Hi, > > I have a Dell P3-500 Optiplex GX1. I was running FreeBSD 5.0 on an 8G drive. > I recently upgraded to a Western Digital ATA100 40GB drive and loaded > FreeBSD 5.1. > I expected to get improved drive performance, however, my motherboard would > only do UDMA-33. > > So, I picked up a Maxtor SATA/150 PCI Combo card. It's supposed to do > ATA-100. My dmesg > indicates that it is running UDMA-100, but my disk dump performance is still > pathetic. > > Here's a dd sample: > > tigger# dd if=/dev/ad8s1d of=/home/chris/tmp.dat count=10000 > 10000+0 records in > 10000+0 records out > 5120000 bytes transferred in 2.292473 secs (2233396 bytes/sec) > > ~ 2MB per second?? It was about 1.8MB per second before I upgraded. The only > thing > I can attribute the marginal speed-up to is the faster drive rotation speed > (7400 RPM). What do you expect when you only transfer 512 bytes with each read/write? That is a lot of overhead, and will make the actual speed of the disk to have little effect on the numbers obtained. Try increasing the block size. I.e. try: dd if=/dev/ad8s1d of=/home/chris/tmp.dat bs=64k count=100 On my system that gives about a factor of 8 faster performance. To get a better idea on how fast the disk actually is (with less overhead from the filesystem, and with less seeking involved) (and also to get bigger numbers :-) ) try sending the output to /dev/null instead of an actual file. (I.e. use of=/dev/null instead of of=/home/chris/tmp.dat) -- <Insert your favourite quote here.> Erik Trulsson ertr1013@student.uu.se --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.408 / Virus Database: 230 - Release Date: 10/24/2002 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.408 / Virus Database: 230 - Release Date: 10/24/2002
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