Date: Sat, 13 Nov 1999 21:34:30 -0500 From: Greg Lehey <grog@mojave.sitaranetworks.com> To: Bernd Walter <ticso@cicely.de>, Mattias Pantzare <pantzer@ludd.luth.se> Cc: freebsd-fs@FreeBSD.ORG Subject: Re: RAID-5 and failure Message-ID: <19991113213430.48370@mojave.sitaranetworks.com> In-Reply-To: <19991106200754.A9682@cicely7.cicely.de>; from Bernd Walter on Sat, Nov 06, 1999 at 08:07:54PM %2B0100 References: <ticso@cicely.de> <199911061827.TAA22113@zed.ludd.luth.se> <19991106200754.A9682@cicely7.cicely.de>
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On Saturday, 6 November 1999 at 20:07:54 +0100, Bernd Walter wrote: > 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. Yes, I suppose we could implement that for maximum security. I wonder if any NOVRAM boards are available. Greg -- 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-fs" in the body of the message
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