From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Al Boldi" Subject: Multiplexed RAID-1 mode Date: Sun, 31 Jul 2005 19:06:47 +0300 Message-ID: <200507311907.WAA07886@raad.intranet> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: 'Gordon Henderson' Cc: linux-raid@vger.kernel.org, 'Jeff Breidenbach' List-Id: linux-raid.ids Gordon Henderson wrote: { On Sat, 30 Jul 2005, Jeff Breidenbach wrote: > > I just ran a Linux software RAID-1 benchmark with some 500GB SATA > drives in NCQ mode, along with a non-RAID control. Details are here > for those interested. > > http://www.jab.org/raid-bench/ The results you get are about what I get on various systems - essentially with RAID-1 you get about the same speed as a single drive will get. ns1:/var/tmp# hdparm -tT /dev/md1 /dev/sda1 /dev/sdb1 /dev/md1: Timing cached reads: 4116 MB in 2.00 seconds = 2058.31 MB/sec Timing buffered disk reads: 174 MB in 3.00 seconds = 57.99 MB/sec /dev/sda1: Timing cached reads: 4096 MB in 2.00 seconds = 2048.31 MB/sec Timing buffered disk reads: 176 MB in 3.03 seconds = 58.11 MB/sec /dev/sdb1: Timing cached reads: 4116 MB in 2.00 seconds = 2057.28 MB/sec Timing buffered disk reads: 176 MB in 3.02 seconds = 58.27 MB/sec } Multiplexing read/write requests would certainly improve performance ala RAID-0 (-offset overhead). During reads the same RAID-0 code (+mirroring offset) could be used. During writes though, this would imply delayed mirroring. -- Al