Date: Sun, 7 Nov 1999 22:39:21 -0500 From: Greg Lehey <grog@lemis.com> To: "Justin T. Gibbs" <gibbs@FreeBSD.ORG>, Kelly Yancey <kbyanc@posi.net> Cc: Bernd Walter <ticso@cicely.de>, Mattias Pantzare <pantzer@ludd.luth.se>, freebsd-fs@FreeBSD.ORG Subject: Re: feature list journalled fs Message-ID: <19991107223921.30116@yana.lemis.com> In-Reply-To: <199911042245.PAA05113@caspian.plutotech.com>; from Justin T. Gibbs on Thu, Nov 04, 1999 at 03:45:26PM -0700 References: <Pine.BSF.4.05.9911041822560.21761-100000@kronos.alcnet.com> <199911042245.PAA05113@caspian.plutotech.com>
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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
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