From owner-freebsd-questions Tue Jul 25 18: 2:57 2000 Delivered-To: freebsd-questions@freebsd.org Received: from wantadilla.lemis.com (wantadilla.lemis.com [192.109.197.80]) by hub.freebsd.org (Postfix) with ESMTP id 4C0A937BCF4 for ; Tue, 25 Jul 2000 18:02:52 -0700 (PDT) (envelope-from grog@wantadilla.lemis.com) Received: (from grog@localhost) by wantadilla.lemis.com (8.9.3/8.9.3) id KAA92371; Wed, 26 Jul 2000 10:32:45 +0930 (CST) (envelope-from grog) Date: Wed, 26 Jul 2000 10:32:44 +0930 From: Greg Lehey To: Meagan Jia Pi Cc: freebsd-questions@FreeBSD.ORG Subject: Re: a newbie RAID5 question Message-ID: <20000726103244.J55913@wantadilla.lemis.com> References: <07f601bff686$39112a20$e293c83f@meagan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.4i In-Reply-To: <07f601bff686$39112a20$e293c83f@meagan>; from meagan@e-lingo.com on Tue, Jul 25, 2000 at 03:18:12PM -0700 Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.lemis.com/~grog X-PGP-Fingerprint: 6B 7B C3 8C 61 CD 54 AF 13 24 52 F8 6D A4 95 EF Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Tuesday, 25 July 2000 at 15:18:12 -0700, Meagan Jia Pi wrote: > Hi All, > > I'd like to test single disk failure recovery a RAID5 system with > FreeBSD installed. But I am not fully convinced that the test will > be successful. I understand that parity is distributed among the > drives, but how can a blank disk be recovered from the other disks? Well, you can read from the array when one disk is missing, so all the code needs to do is: 1. If the block to be replaced is a data block, read it from the array and write it back to the drive. 2. If it's a parity block, read the band and create the parity from it. See /usr/src/sys/dev/vinum/vinumrevive.c, function revive_block, for how this is implemented for Vinum. Greg -- When replying to this message, please copy the original recipients. For more information, see http://www.lemis.com/questions.html 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-questions" in the body of the message