Date: Tue, 14 Jul 1998 20:05:16 +0200 (CEST) From: Wilko Bulte <wilko@yedi.iaf.nl> To: grog@lemis.com (Greg Lehey) Cc: tlambert@primenet.com, gibbs@plutotech.com, andre@pipeline.ch, Matthew.Alton@anheuser-busch.com, Hackers@FreeBSD.ORG Subject: Re: Software RAID-5 performance Message-ID: <199807141805.UAA03774@yedi.iaf.nl> In-Reply-To: <19980714122952.L754@freebie.lemis.com> from Greg Lehey at "Jul 14, 98 12:29:52 pm"
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As Greg Lehey wrote... > (trimming -fs) > > Software RAID is a data integrity issue, not a performance one, > > and I think making the performance argument for whatever reason > > (protection domain crossing, interleaved I/O, SMP scalability, > > etc.) is a strawman at best. > > I'm not sure that I understand what you're saying here. Obviously > offloading the checksum calculation (or anything else, for that > matter) to an external box will offload the CPU. And I can't see any > particular difference in data integrity between the two approaches. Software raid without stable (battery backed) storage is flawed: assume a write that had 2 disks actually write the data onto the platter and (e.g.) the parity data did not make it out on it's platter because your system crashed. Or the power went bang. Or... You now have an inconsistent raid5 set. Wilko _ ______________________________________________________________________ | / o / / _ Bulte email: wilko @ yedi.iaf.nl |/|/ / / /( (_) Arnhem, The Netherlands WWW: http://www.tcja.nl ______________________________________________ Powered by FreeBSD __________ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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