From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ross Vandegrift Subject: Re: RAID 5 performance problems Date: Thu, 3 Apr 2003 13:47:56 -0500 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20030403184756.GA7971@willow.seitz.com> References: <73300040777B0F44B8CE29C87A0782E101FA97B2@exchange.explainerdc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: To: "Peter L. Ashford" Cc: Jonathan Vardy , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-raid.ids [CC list trimmed] On Thu, Apr 03, 2003 at 10:05:27AM -0800, Peter L. Ashford wrote: > > 4 of the raid HD's are connected to the Promise controller and the other > > raid HD is master on the second onboard IDE channel (udma2/ATA33) > > I've NEVER heard that the FastTrak runs fast (I have been told that they > run VERY slowly). The FastTrack cards are identical to the UltraDMA cards from promise - you can turn one into the other with a resistor and a firmware flash. > I've benchmarked RAW disk speeds with an Ultra-100 and > WD1200JB drives, and gotten 50MB/S from each disk, as opposed to your > 26MB/S (there should be almost no difference for the BB drives). Makes perfect sense - he's getting 50M/s to each channel, but it's split over two drives, so drive throughput is about halved. > Use one disk per channel > (Master only), and move the system disk onto one of the Promise cards. Absolutely correct - you should *never* run IDE RAID on a channel that has both a master and slave. When one disk on an IDE channel has an error, the whole channel is reset - this makes both disks inaccessible, and RAID5 now has two failed disks => you data is gone! *ALWAYS* use separate IDE channels. -- Ross Vandegrift ross@willow.seitz.com A Pope has a Water Cannon. It is a Water Cannon. He fires Holy-Water from it. It is a Holy-Water Cannon. He Blesses it. It is a Holy Holy-Water Cannon. He Blesses the Hell out of it. It is a Wholly Holy Holy-Water Cannon. He has it pierced. It is a Holey Wholly Holy Holy-Water Cannon. He makes it official. It is a Canon Holey Wholly Holy Holy-Water Cannon. Batman and Robin arrive. He shoots them.