From owner-freebsd-fs Sat Nov 6 11: 8: 5 1999 Delivered-To: freebsd-fs@freebsd.org Received: from mail.du.gtn.com (mail.du.gtn.com [194.77.9.57]) by hub.freebsd.org (Postfix) with ESMTP id CF03C14BDC for ; Sat, 6 Nov 1999 11:08:02 -0800 (PST) (envelope-from ticso@mail.cicely.de) Received: from mail.cicely.de (cicely.de [194.231.9.142]) by mail.du.gtn.com (8.9.3/8.9.3) with ESMTP id UAA03422; Sat, 6 Nov 1999 20:01:12 +0100 (MET) Received: (from ticso@localhost) by mail.cicely.de (8.9.0/8.9.0) id UAA09809; Sat, 6 Nov 1999 20:07:54 +0100 (CET) Date: Sat, 6 Nov 1999 20:07:54 +0100 From: Bernd Walter To: Mattias Pantzare Cc: Bernd Walter , freebsd-fs@FreeBSD.ORG Subject: Re: RAID-5 and failure Message-ID: <19991106200754.A9682@cicely7.cicely.de> References: <199911061827.TAA22113@zed.ludd.luth.se> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0pre3i In-Reply-To: <199911061827.TAA22113@zed.ludd.luth.se> Sender: owner-freebsd-fs@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Sat, Nov 06, 1999 at 07:27:20PM +0100, Mattias Pantzare wrote: > > If the system panics or power fails between such a write there is no way to > > find out if the parity is broken beside verifying the complete plex after > > reboot - the problem should be the same with all usual hard and software > > solutions - greg already begun or finished recalculating and checking the > > parity. > > This is realy a optimisation issue, if you just write without using > two-phase commit then you have to recalculate parity after a powerfailure. > (One might keep track of the regions of the disk that have had writes latly > and only recalculate them) > > Or you do as it says under Two-phase commitment in > http://www.sunworld.com/sunworldonline/swol-09-1995/swol-09-raid5-2.html. > That's exactly what vinum does at this moment but without the log. You need persistent memory for this such as nv-memory or a log area on any disk. nv-memory on PCs is usually to small and maybe to slow for such purposes. I asume that a log area on any partitipating disk is not a good idea. On a different disk it would be an option but still needs implementation. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message