From owner-freebsd-current Sat Jan 31 17:32:10 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id RAA18479 for current-outgoing; Sat, 31 Jan 1998 17:32:10 -0800 (PST) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from allegro.lemis.com (allegro.lemis.com [192.109.197.134]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id RAA18410 for ; Sat, 31 Jan 1998 17:31:59 -0800 (PST) (envelope-from grog@lemis.com) Received: from freebie.lemis.com (freebie.lemis.com [192.109.197.137]) by allegro.lemis.com (8.8.7/8.8.5) with ESMTP id LAA29472; Sun, 1 Feb 1998 11:59:40 +1030 (CST) Received: (from grog@localhost) by freebie.lemis.com (8.8.8/8.8.7) id LAA07858; Sun, 1 Feb 1998 11:59:39 +1030 (CST) (envelope-from grog) Message-ID: <19980201115938.38542@lemis.com> Date: Sun, 1 Feb 1998 11:59:38 +1030 From: Greg Lehey To: Karl Denninger Cc: Jonathan Lemon , Brian Tao , current@FreeBSD.ORG Subject: Re: RAID controllers - folks, check this thing out References: <19980131144604.03410@mcs.net> <19980131155527.19192@mcs.net> <19980131160423.30536@right.PCS> <19980131185203.60841@mcs.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.84e In-Reply-To: <19980131185203.60841@mcs.net>; from Karl Denninger on Sat, Jan 31, 1998 at 06:52:03PM -0600 Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-41-739-7062 WWW-Home-Page: http://www.lemis.com/~grog 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 06:52:03PM -0600, Karl Denninger wrote: > On Sat, Jan 31, 1998 at 04:04:24PM -0600, Jonathan Lemon wrote: >> On Jan 01, 1998 at 03:55:27PM -0600, Karl Denninger wrote: >>> RAID 5, due to the way it stripes parity across the volumes, has a "sweet >>> spot" in performance at 5 spindles. >> >> This is only true if your stripe set is 4 spindles. There's nothing >> wrong with using a stripe set of 8 spindles (9 devices), except that >> it tends to make small writes slower, since your data is spread out >> over more devices. >> >> 5 devices is not an inherent property of RAID 5, AFAIK. >> -- >> Jonathan > > The trade-off, however, between slowing down write performance, parity > computation, stripe size, etc seems to be right around 5 spindles. You can't say this without making assumptions about the nature of your access. What if it's 99.9% read access? What if it's 60% write access? Greg