Date: Fri, 19 Nov 1999 18:50:59 +0100 (CET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: rjesup@wgate.com Cc: freebsd-fs@FreeBSD.ORG Subject: Re: RAID-5 and failure Message-ID: <199911191750.SAA54691@yedi.iaf.nl> In-Reply-To: <ybuso22qw3t.fsf@jesup.eng.tvol.net.jesup.eng.tvol.net> from Randell Jesup at "Nov 19, 1999 11:33:58 am"
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As Randell Jesup wrote ... > Greg Lehey <grog@mojave.sitaranetworks.com> writes: [...] > >2. Get an NVRAM board and use it for this purpose. > > How much is commonly stored in nvram boards for raid? If it's > merely the location of the write, _maybe_ clock-chip memory might work > (if writing to it that often doesn't slow down the system - I don't > remember how fast the interface is). If it's the entire sector, well then > we're screwed without it or #3 - or rather we could have a corrupted > stripe after a crash. Oh well. Well, I can tell you that the HSx DEC ^H^H^H Compaq controllers use the battery backup-ed writeback cache for this purpose. These are anything from 32 to 512Mb per controllers. Controllers generally are used in redundant pairs, each with their own cache module, each cachemodule with it's own backup battery. To avoid the potential for datacorruption when a cache module fails they can be setup to run in mirrored cache mode. Price? I'm pretty sure you don't want to know ;-) The SCSI variants work fine on FreeBSD BTW. I have yet to try the Fibrechannel boxes. I lack a host adapter that FreeBSD has a driver for. Wilko -- | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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