From owner-freebsd-current Sat Jan 31 16:54:57 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id QAA11722 for current-outgoing; Sat, 31 Jan 1998 16:54:57 -0800 (PST) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from Kitten.mcs.com (Kitten.mcs.com [192.160.127.90]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id QAA11713 for ; Sat, 31 Jan 1998 16:54:55 -0800 (PST) (envelope-from karl@Mars.mcs.net) Received: from Mars.mcs.net (karl@Mars.mcs.net [192.160.127.85]) by Kitten.mcs.com (8.8.7/8.8.2) with ESMTP id SAA07232; Sat, 31 Jan 1998 18:54:54 -0600 (CST) Received: (from karl@localhost) by Mars.mcs.net (8.8.7/8.8.2) id SAA24022; Sat, 31 Jan 1998 18:54:54 -0600 (CST) Message-ID: <19980131185454.07579@mcs.net> Date: Sat, 31 Jan 1998 18:54:54 -0600 From: Karl Denninger To: Brian Tao Cc: current@FreeBSD.ORG Subject: Re: RAID controllers - folks, check this thing out References: <19980131155527.19192@mcs.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.84 In-Reply-To: ; from Brian Tao on Sat, Jan 31, 1998 at 05:25:45PM -0500 Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG X-To-Unsubscribe: mail to majordomo@FreeBSD.org "unsubscribe current" On Sat, Jan 31, 1998 at 05:25:45PM -0500, Brian Tao wrote: > On Sat, 31 Jan 1998, Karl Denninger wrote: > > > > RAID 5, due to the way it stripes parity across the volumes, has a > > "sweet spot" in performance at 5 spindles. > > What "way" is that? On a given stripe, one drive provides the > parity block, the choice of drive staggered across consecutive > stripes. There may be an issue with small, sequential writes on a > RAID 5 set with a large number of drives, but I can't think of any > reason why five drives should be magical. > -- > Brian Tao (BT300, taob@netcom.ca) > "Though this be madness, yet there is method in't" A single write which does not consume an entire stripe requires that the entire stripe be READ FIRST in order to recompute parity. The more spindles involved in a stripe, the larger the write must be before this happens, and the worse the penalty if it does not. -- -- Karl Denninger (karl@MCS.Net)| MCSNet - Serving Chicagoland and Wisconsin http://www.mcs.net/ | T1's from $600 monthly to FULL DS-3 Service | NEW! K56Flex support on ALL modems Voice: [+1 312 803-MCS1 x219]| EXCLUSIVE NEW FEATURE ON ALL PERSONAL ACCOUNTS Fax: [+1 312 803-4929] | *SPAMBLOCK* Technology now included at no cost