Date: Sat, 03 Jan 2004 16:54:47 -0800 From: Bohdan Tashchuk <tashchuk@easystreet.com> To: freebsd-hardware@freebsd.org Cc: d.ortiz@in.ilimit.es Subject: Re: atacontrol/udma Message-ID: <3FF76457.4070700@easystreet.com> In-Reply-To: <3FF62760.1030302@covad.net> References: <3FF62760.1030302@covad.net>
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Dan Strick wrote: > I don't know why your I/O benchmarks report only 32 MB/sec. Perhaps > this is natural for these benchmarks and your particular drives. > You might try "dd if=/dev/ad0 of=/dev/null bs=128k" while running > "iostat 5". (The 128k buffer size may be necessary.) I get about > 56 MB/sec even though the driver thinks it has configured the drive > for UDMA33. This might not be related to original problem, but I've seen an approx 2:1 disk transfer speed ratio on various IDE drives from outer tracks to inner tracks. On the outside I've seen close to 60 MB/sec using dd but this slows to about 30 MB/sec on inner tracks. Also in my experience with FreeBSD 4.x it IS necessary to set a buffer size when using dd. The default is very small. But setting something larger than the 128k max of raw IDE, for example bs=1024k, seems to be OK.
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