From owner-freebsd-hackers Tue Oct 27 23:39:06 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id XAA00543 for freebsd-hackers-outgoing; Tue, 27 Oct 1998 23:39:06 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from aurora.sol.net (aurora.sol.net [206.55.65.76]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id XAA00538 for ; Tue, 27 Oct 1998 23:39:05 -0800 (PST) (envelope-from jgreco@aurora.sol.net) Received: (from jgreco@localhost) by aurora.sol.net (8.8.8/8.8.8/SNNS-1.02) id BAA10774 for hackers@freebsd.org; Wed, 28 Oct 1998 01:38:26 -0600 (CST) From: Joe Greco Message-Id: <199810280738.BAA10774@aurora.sol.net> Subject: Re: Multi-terabyte disk farm In-Reply-To: <3.0.3.32.19981028011701.0070082c@bugs.us.dell.com> from Tony Overfield at "Oct 28, 98 01:17:01 am" To: hackers@FreeBSD.ORG Date: Wed, 28 Oct 1998 01:38:26 -0600 (CST) X-Mailer: ELM [version 2.4ME+ PL32 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > At 11:00 PM 10/27/98 -0600, you wrote: > >Writing to a RAID involves a performance penalty where all drives have to > >participate in the write process. Involving only five drives instead of > >eight implies that the other three can be doing something else. > > Why would you ever need to write to _all_ of the drives, unless you are > writing an entire data-stripe's worth of data, in which case you'll be > writing to at least that many drives anyway? Never mind, I was thinking of parity regeneration. Too much other stuff going on in my head right now. I was thinking of the specific case where you need to read the other drives in order to calculate the parity. Assuming an initialized RAID, that's an invalid assumption, although you still have to read/write two blocks in that case. There's something else that's nagging at my memory... (I'm spending my day moving 8 million files, so disks are certainly the only thing on my mind right now) ... Joe ------------------------------------------------------------------------------- Joe Greco - Systems Administrator jgreco@ns.sol.net Solaria Public Access UNIX - Milwaukee, WI 414/342-4847 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message