Date: Mon, 22 Mar 1999 09:24:17 +1030 From: Greg Lehey <grog@lemis.com> To: Tom <tom@sdf.com> Cc: Nick Hilliard <nick@iol.ie>, freebsd-scsi@FreeBSD.ORG Subject: Re: dpt raid-5 performance Message-ID: <19990322092417.U429@lemis.com> In-Reply-To: <Pine.BSF.4.05.9903211333100.24283-100000@misery.sdf.com>; from Tom on Sun, Mar 21, 1999 at 01:38:09PM -0800 References: <19990322090015.S429@lemis.com> <Pine.BSF.4.05.9903211333100.24283-100000@misery.sdf.com>
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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
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