Date: Sat, 6 Nov 1999 20:07:54 +0100 From: Bernd Walter <ticso@cicely.de> To: Mattias Pantzare <pantzer@ludd.luth.se> Cc: Bernd Walter <ticso@cicely.de>, freebsd-fs@FreeBSD.ORG Subject: Re: RAID-5 and failure Message-ID: <19991106200754.A9682@cicely7.cicely.de> In-Reply-To: <199911061827.TAA22113@zed.ludd.luth.se> References: <ticso@cicely.de> <199911061827.TAA22113@zed.ludd.luth.se>
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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
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