From owner-freebsd-scsi Sun Mar 21 15: 2: 7 1999 Delivered-To: freebsd-scsi@freebsd.org Received: from allegro.lemis.com (allegro.lemis.com [192.109.197.134]) by hub.freebsd.org (Postfix) with ESMTP id 312F714E11 for ; Sun, 21 Mar 1999 15:02:03 -0800 (PST) (envelope-from grog@freebie.lemis.com) Received: from freebie.lemis.com (freebie.lemis.com [192.109.197.137]) by allegro.lemis.com (8.9.1/8.9.0) with ESMTP id JAA13723; Mon, 22 Mar 1999 09:24:17 +1030 (CST) Received: (from grog@localhost) by freebie.lemis.com (8.9.3/8.9.0) id JAA07228; Mon, 22 Mar 1999 09:24:17 +1030 (CST) Message-ID: <19990322092417.U429@lemis.com> Date: Mon, 22 Mar 1999 09:24:17 +1030 From: Greg Lehey To: Tom Cc: Nick Hilliard , freebsd-scsi@FreeBSD.ORG Subject: Re: dpt raid-5 performance References: <19990322090015.S429@lemis.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.93.2i In-Reply-To: ; from Tom on Sun, Mar 21, 1999 at 01:38:09PM -0800 WWW-Home-Page: http://www.lemis.com/~grog Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-41-739-7062 Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Sunday, 21 March 1999 at 13:38:09 -0800, Tom wrote: > > On Mon, 22 Mar 1999, Greg Lehey wrote: > >> On Sunday, 21 March 1999 at 12:54:23 -0800, Tom wrote: >>> >>> On Sun, 21 Mar 1999, Greg Lehey wrote: >>> >>>>> FreeBSD will likely never send IOs big enough for the strip size of >>>>> 512kb to ever be useful. >>>> >>>> It does. The largest I/O transfer is 64 kB. You don't want to >>>> fragment requests, because that increases the I/O load on the array. >>> >>> At the cost of single-process performance. >> >> I don't know what you mean here. Can you explain that statement? > > Small strip sizes are good for single-user situations (like running > Bonnie), because the IO load will be split over all drives. Did you read my message refuting this claim? If so, what are your arguments against it? > Large strip sizes are good for multi-user situations, where the > extra overhead of the transactions becomes a problem. What does that mean? Which transaction? We're talking disk transfers here. > DPT starts with a default of 16KB for the strip size. Until > recently, it couldn't be increased over 64KB. I've used these cards > quite extensively under FreeBSD. Remember what is good for DPT > cards is not always what is good for other systems, particularly > software solutions. Yes, that's what I suggest in my long performance analysis message. Greg -- See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message