From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Freemyer Subject: Re: IDE channels not independent in PIIX4E? Date: Fri, 25 Feb 2005 09:45:37 -0500 Message-ID: <87f94c37050225064563f663c5@mail.gmail.com> References: Reply-To: Greg Freemyer Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received: from wproxy.gmail.com ([64.233.184.201]:28035 "EHLO wproxy.gmail.com") by vger.kernel.org with ESMTP id S262711AbVBYOpi (ORCPT ); Fri, 25 Feb 2005 09:45:38 -0500 Received: by wproxy.gmail.com with SMTP id 68so465023wra for ; Fri, 25 Feb 2005 06:45:38 -0800 (PST) In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: GrantC Cc: linux-ide@vger.kernel.org I can't speak to your specific motherboard/chipset, but the performance testing I have done shows that the onboard IDE controllers do not have two independent channels, so using both channels does not provide twice the speed of a single channel, not even close. True under both Linux and Windows2K. OTOH, I have tested 3 or 4 PCI-based Dual Channel IDE controllers and they work much better from a performance perspective. I recently tested both the SIIG dual-channel card and Adaptec dual-channel card. They were both in the $50-$60 range and neither has given me any problems, but I have heard people complain about the SIIG. HTH Greg On Fri, 25 Feb 2005 16:47:46 +1100, GrantC wrote: > Greetings, > > I have an old but reliable Intel SE440BX-2 with 440BX and PIIX4E > chipset. 120 + 80 GB hard drives on each channel as master, very > disappointing md software RAID0 or RAID1 performance. > > Slackware 10.1 with 2.4.29 or 2.4.30pre2, testing back to 2.4.21. > > One thing I noticed is that if I start a > > dd if=/dev/zero bs=4k of=/dev/hdX > > on each drive, then Ctrl-C stop each, one terminal will wait for > the other drive to complete the write before starting its turn > to complete the pending write. > > It seems that somewhere what I expected to be two parallel data > streams are serialised. As the chipset only does udma33 I was > hoping to get an OS performance gain with RAID0. Box has 512MB > memory and rarely touches swap. > > Is this a limit of the hardware or did I miss some kernel tuning? > > Have benchmarked with tiobench -- that tells me chunk-size has > little effect, software RAID costs about 8% CPU, and sequential > writes cost roughly 20%, 40% and 60% for ext2, ext3 and reiserfs. > > Filesystem sequential read speed improved from 17 to 25 MB/s for > RAID0, but no improvement in write speed. > > Raw (non-filesystem) dd speeds are about 27MB/s read, 20MB/s write > to non-RAID partition. All testing done on same partitions, so > no confusion with fast or slow end of drive. The drives are > Seagate 7200.7 series with 2MB cache. > > Any pointers on tuning options appreciated, the Intel datasheets > don't really tell me much. As for reading the kernel source, I > have no idea where to start, not much under Docs, and I dunno > which or which way to turn the 'knobs'. > > Even search terms would be welcome :) > > Thanks, > Grant. > > - > To unsubscribe from this list: send the line "unsubscribe linux-ide" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >