From owner-freebsd-fs Mon Nov 8 7: 6:55 1999 Delivered-To: freebsd-fs@freebsd.org Received: from mojave.sitaranetworks.com (mojave.sitaranetworks.com [199.103.141.157]) by hub.freebsd.org (Postfix) with ESMTP id BC81B14CA9; Mon, 8 Nov 1999 07:06:50 -0800 (PST) (envelope-from grog@mojave.sitaranetworks.com) Message-ID: <19991107223921.30116@yana.lemis.com> Date: Sun, 7 Nov 1999 22:39:21 -0500 From: Greg Lehey To: "Justin T. Gibbs" , Kelly Yancey Cc: Bernd Walter , Mattias Pantzare , freebsd-fs@FreeBSD.ORG Subject: Re: feature list journalled fs Reply-To: Greg Lehey References: <199911042245.PAA05113@caspian.plutotech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <199911042245.PAA05113@caspian.plutotech.com>; from Justin T. Gibbs on Thu, Nov 04, 1999 at 03:45:26PM -0700 Sender: owner-freebsd-fs@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Thursday, 4 November 1999 at 15:45:26 -0700, Justin T. Gibbs wrote: >> On Thu, 4 Nov 1999, Greg Lehey wrote: >> >>> That's for writing. When throughput becomes the limit, the write >>> throughput of RAID-4 is limited to about 2 / n of the write throughput >>> of RAID-5. On reading (randomly), it's (n - 1) / n. >> >> I think that it has been significantly proven that RAID 4 is not very >> userful, and I regret bringing it up...sometimes the mind wonders :). > > It all depends on your application. If you are dealing with a data > set composed of large, fixed sized entries, RAID 3 or 4 (they are almost > identical) will always outperform RAID5. I assume you're talking about read access, and by "large" you mean "more than one stripe". Under these circumstances, I can believe that sometimes you'll see better performance when you have few requestors. My discussion applied to multiple requestors. I don't think you can generalize, though I'm prepared to listen to detailed arguments, and even more to benchmark results :-) Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message