Date: Wed, 11 Jul 2012 00:49:34 -0700 (PDT) From: Jason Usher <jusher71@yahoo.com> To: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> Cc: freebsd-fs@freebsd.org Subject: Re: vdev/pool math with combined raidzX vdevs... Message-ID: <1341992974.53118.YahooMailClassic@web122503.mail.ne1.yahoo.com> In-Reply-To: <alpine.GSO.2.01.1207101905120.27589@freddy.simplesystems.org>
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Hello Bob, --- On Tue, 7/10/12, Bob Friesenhahn <bfriesen@simple.dallas.tx.us> wrote: > > Am I really the only person worrying about the > interactive failure properties of combining vdevs into a > pool ? > > Yes. You are the only one. The strength of the > individual vdev is the primary determining factor of the > strength of the pool. Thanks for responding. So I must be mistaken, and the failure probability of each vdev is not additive ? As I mentioned earlier in the thread, I am not a probability person, nor would I trust my own calculations if I tried. Because if it is additive, combining vdevs erases about half of the difference between raidz2 and raidz3, which I think is fairly significant. Can we at least agree that it's not the same as a lone vdev ? If I can destroy a vdev by blowing 4 disks in it, OR by blowing 4 disks in some other vdev, that's a higher risk than if it were alone...home | help
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