Date: Mon, 18 Oct 2004 20:09:39 +0200 From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@DeepCore.dk> To: fandino@ng.fadesa.es Cc: freebsd-current@freebsd.org Subject: Re: FreeBSD 5.3b7and poor ata performance Message-ID: <417406E3.9010706@DeepCore.dk> In-Reply-To: <4173F2E9.7010407@ng.fadesa.es> 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>
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fandino wrote: > Hello Søren, > > I was running FreeBSD-4.x for two years with this problem, waiting > for FreeBSD-5 because ATAng looks very promising. > > Unfortunately the performance problem persist :-( and I'd like to > call the attention about performance over raw devices, whilst it's > a very scientific test it's very curious: > > # dd if=/dev/ad4 of=/dev/null bs=1024k count=1024 > 1024+0 records in > 1024+0 records out > 1073741824 bytes transferred in 31.090536 secs (34535970 bytes/sec) > > over 34000 K/sec, using raw devices (for sequential access obviously) > not softupdates, filesystems or caches are involved, and with all this > FreeBSD performace is very deficient. Tests with OpenBSD and Linux > using raw devices shows a throughput of approx 60000 K/sec. > The question here is why using low-level access to disks is so bad? I need more info on your system, ie config file dmesg etc. From what you've posted so far I've setup a system with a semilar disk etc, and I get this: dd if=/dev/ad10 of=/dev/null bs=1024k count=1024 1024+0 records in 1024+0 records out 1073741824 bytes transferred in 18.488903 secs (58074934 bytes/sec) On a WDC 70G raptor you will see: # dd if=/dev/ad4 of=/dev/null bs=1024k count=1024 1024+0 records in 1024+0 records out 1073741824 bytes transferred in 14.956484 secs (71791059 bytes/sec) So there is nothing in FreeBSD-5.3 thats hindering performance in the ATA subsystem as far as I can measure. > Perphas I'm missing something but this seems very weird to me. Most likely, as the result I get are close to what the disks can deliver. > I'd like to know wich is you opinion about this. If you run a stock generic kernel with the debug (WITNESS etc) taken out you should see the same raw performance as I do. Now, raw performance is one thing, filesystem I/O something entirely different and not within my area of expertise. I do know that much though, that its very difficult to measure in a way that makes comparison between the different systems possible or even fair. -- -Sørenhelp
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