From owner-freebsd-current Mon Dec 10 10:49:37 2001 Delivered-To: freebsd-current@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id F340A37B419; Mon, 10 Dec 2001 10:49:34 -0800 (PST) Received: (from dillon@localhost) by apollo.backplane.com (8.11.6/8.9.1) id fBAInSO47847; Mon, 10 Dec 2001 10:49:28 -0800 (PST) (envelope-from dillon) Date: Mon, 10 Dec 2001 10:49:28 -0800 (PST) From: Matthew Dillon Message-Id: <200112101849.fBAInSO47847@apollo.backplane.com> To: Wilko Bulte Cc: Mike Smith , Terry Lambert , Joerg Wunsch , freebsd-current@FreeBSD.ORG Subject: Re: cvs commit: src/sys/kern subr_diskmbr.c References: <200112101754.fBAHsRV01202@mass.dis.org> <200112101813.fBAIDKo47460@apollo.backplane.com> <20011210192251.A65380@freebie.xs4all.nl> Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG :For RAID3 that is true. For the other ones... : :> performance without it - for reading OR writing. It doesn't matter :> so much for RAID{1,10}, but it matters a whole lot for something like :> RAID-5 where the difference between a spindle-synced read or write :> and a non-spindle-synched read or write can be upwards of 35%. : :If you have RAID5 with I/O sizes that result in full-stripe operations. : :-- :| / o / /_ _ email: wilko@FreeBSD.org :|/|/ / / /( (_) Bulte Arnhem, The Netherlands Well, for reads a non-stripe-crossing op would still work reasonably well. But for writes less then full-stripe operations without spindle sync are going to be terrible due to the read-before-write requirement (to calculate parity). The disk cache is useless in that case. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message