Date: Thu, 20 Jan 2005 20:00:39 +0100 From: Emanuel Strobl <emanuel.strobl@gmx.net> To: freebsd-stable@freebsd.org Subject: Re: Higher ATA-Mode -> lower speed Message-ID: <200501202000.43688.emanuel.strobl@gmx.net> In-Reply-To: <200501201948.42707.emanuel.strobl@gmx.net> References: <200501201948.42707.emanuel.strobl@gmx.net>
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[-- Attachment #1 --] Am Donnerstag, 20. Januar 2005 19:48 schrieb Emanuel Strobl: > Dear ata interested guys, > > I observed a strange behaviour which seems to explain my often noticed > "16MB/s hard-limit" > > I have a UDMA133 drive (MAXTOR 6L060J3) which saturates at 16MB/s when I > dump anything to it, regardless of the block size. This transfer rate is > reached with bs=4k and doesn't increase any more even not with bs=64k. > > Now, when I set the mode to UDMA100 I get well over 40MB/s!!!! > > Can anybody confirm that for different hw? Especially people like fandino > who already discussed poor ata performance on -current (~16 Oct. 04). I can confirm that for my workstation here. i815 chipset and seagate ST380011A. When set to UDMA100 (the maximum) the following dump gives 16MB/s 'dd if=/dev/zero of=/usr/testfile bs=16k count=2000). When I limit the mode to UDMA66 I get 53MB/s !!!!!!!!!!!!!!!! It seems that's independent of UDMA133 instead it's when mode is set to the maximum the chipset can handle! This really hurts! But it's _the_ eplanation for all the "poor ata performance" reports. -Harry > > Why does UDMA133 mode limit the transfer speed so badly? And why do I get > significantly slower transfer rates (32MB/s insted of 42MB/s) when I set > the mode to UDMA66 (compared to UDMA100 but twice the speed of UDMA133)? > There's only one device on the channel, so UDMA66 should be fine for > 42MB/s. The controller is a HPT372. > > Best regards, > > -Harry [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (FreeBSD) iD8DBQBB7//bBylq0S4AzzwRArKYAJ4mtS4/I7cpUnqvIrLzgO/MpWIe6gCff7WP pHaAdinpIqJ34qpEI25zd/U= =rO5Y -----END PGP SIGNATURE-----
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