Date: Fri, 12 Dec 1997 18:51:59 +0100 (MET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: tom@sdf.com (Tom) Cc: walcaraz@indy3.gstone.com, freebsd-scsi@FreeBSD.ORG Subject: Re: RAID on FreeBSD Message-ID: <199712121752.SAA01171@yedi.iaf.nl> In-Reply-To: <Pine.BSF.3.95q.971211150053.17850B-100000@misery.sdf.com> from "Tom" at Dec 11, 97 03:04:51 pm
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As Tom wrote... > On Thu, 11 Dec 1997, Wilko Bulte wrote: > > > > 9 drives in an uncomfortable number for RAID5. Probably better to go > > > > Why would 9 drives be uncomfartable? > > Well, if you are going to making one arrray of 9 drives, write > performance will bad. If you are going to making 3 arrays of 3 Why? Calculating the parity takes the same overhead in both cases. What you *don't* want to do is put too many drives of the same raidset on a single SCSI bus. Preferably you have only one drive of each set on each channel. This allows a channel to die completely without loosing your data. > drives each, you will end up with a lot of overhead. > > RAID5 arrays of 5 drives is kinda of nice sweet spot. If you go much > bigger, just use RAID0 over multiple RAID5. I don't agree. It *really* depends on the hardware you're using. E.g the company I work for (DEC) sells the HSZx0 range of controllers. This controller has (along with battery backup writeback cache) 6 SCSI device buses. The 'natural' number for that one is 6 drives. Generally my point is that you really have to take a very close look to your hardware setup. Wilko _ ______________________________________________________________________ | / o / / _ Bulte email: wilko @ yedi.iaf.nl http://www.tcja.nl/~wilko |/|/ / / /( (_) Arnhem, The Netherlands - Do, or do not. There is no 'try' ---------------- Support your local daemons: run [Free,Net]BSD Unix ------
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