Date: Thu, 5 Jul 2012 18:16:42 -0700 (PDT) From: Jason Usher <jusher71@yahoo.com> To: freebsd-fs@freebsd.org Subject: vdev/pool math with combined raidzX vdevs... Message-ID: <1341537402.58301.YahooMailClassic@web122504.mail.ne1.yahoo.com>
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It's easy to find the failure math for raidz2 and raidz3. But what if you create a pool with 3 different raidz3 vdevs inside of it ? For instance, 3 12-drive raidz3 vdevs in one big pool. For each individual vdev the failure probability is now higher, since not only will it fail when 4 drives in the vdev fail, but it will also fail if four drives in any of the other two vdevs fail. So each raidz3 vdev now has a failure rate higher than vanilla raidz3 ... but what is that new failure rate ? Is it still higher than vanilla raidz2 ?
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