From: David Taylor <davidt@yadt.co.uk>
To: Stan Hoeppner <stan@hardwarefreak.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: Triple parity and beyond
Date: Fri, 22 Nov 2013 14:19:47 +0000 [thread overview]
Message-ID: <20131122141946.GA18625@yadt.co.uk> (raw)
In-Reply-To: <528F17FB.60909@hardwarefreak.com>
On Fri, 22 Nov 2013, Stan Hoeppner wrote:
>
> With
> any mirror based array one can lose half the disks as long as no two are
> in one mirror. The probability of a pair failing together is very low,
> and this probability decreases even further as the number of drives in
> the array increases. This is one of the many reasons RAID 10 has been
> so popular for so many years.
Er, no.
Sure, the probability of "the failed drive's pair" failing decreases
as the number of drives in the array increases IF you assume there will
be exactly one failure.
But adding more drives increases the probability of another drive
failure, and cancels that out.
Quite obviously adding more unrelated drives to an array does not
affect the probability of failure of the pre-existing drives!
(Except perhaps, by over-stressing the PSU and increasing the
chances of all the drives failing)
--
David Taylor
next prev parent reply other threads:[~2013-11-22 14:19 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-18 22:08 Triple parity and beyond Andrea Mazzoleni
2013-11-18 22:12 ` H. Peter Anvin
2013-11-18 22:35 ` Andrea Mazzoleni
2013-11-18 23:25 ` H. Peter Anvin
2013-11-19 10:16 ` David Brown
2013-11-19 17:36 ` Andrea Mazzoleni
2013-11-19 22:51 ` Drew
2013-11-20 0:54 ` Chris Murphy
2013-11-20 1:23 ` John Williams
2013-11-20 10:35 ` David Brown
2013-11-20 10:31 ` David Brown
2013-11-20 18:09 ` John Williams
2013-11-20 18:44 ` Andrea Mazzoleni
2013-11-21 6:15 ` Stan Hoeppner
2013-11-21 8:32 ` David Brown
2013-11-20 18:34 ` Andrea Mazzoleni
2013-11-20 18:43 ` H. Peter Anvin
2013-11-20 18:56 ` Andrea Mazzoleni
2013-11-20 18:59 ` H. Peter Anvin
2013-11-20 21:21 ` Andrea Mazzoleni
2013-11-20 19:00 ` H. Peter Anvin
2013-11-20 21:04 ` Andrea Mazzoleni
2013-11-20 21:06 ` H. Peter Anvin
2013-11-21 8:36 ` David Brown
2013-11-19 17:28 ` Andrea Mazzoleni
2013-11-19 20:29 ` Ric Wheeler
2013-11-20 16:16 ` James Plank
2013-11-20 19:05 ` Andrea Mazzoleni
2013-11-20 19:10 ` H. Peter Anvin
2013-11-20 20:30 ` James Plank
2013-11-20 21:23 ` Andrea Mazzoleni
2013-11-27 2:50 ` ronnie sahlberg
2013-11-20 21:28 ` H. Peter Anvin
2013-11-21 1:28 ` Stan Hoeppner
2013-11-21 2:46 ` John Williams
2013-11-21 6:52 ` Stan Hoeppner
2013-11-21 7:05 ` John Williams
2013-11-21 22:57 ` Stan Hoeppner
2013-11-21 23:38 ` John Williams
2013-11-22 9:35 ` Stan Hoeppner
2013-11-22 11:24 ` joystick
2013-11-22 15:01 ` John Williams
2013-11-22 22:28 ` Stan Hoeppner
2013-11-22 23:07 ` NeilBrown
2013-11-23 3:46 ` Stan Hoeppner
2013-11-23 5:04 ` NeilBrown
2013-11-23 5:34 ` John Williams
2013-11-23 7:12 ` NeilBrown
2013-11-24 4:03 ` Stan Hoeppner
2013-11-24 5:14 ` John Williams
2013-11-24 21:13 ` Stan Hoeppner
2013-11-24 23:28 ` Rudy Zijlstra
2013-11-24 23:53 ` Alex Elsayed
2013-11-25 2:04 ` Stan Hoeppner
2013-11-25 4:48 ` Alex Elsayed
2013-11-25 9:15 ` David Brown
2013-11-24 5:19 ` Russell Coker
2013-11-24 21:44 ` Stan Hoeppner
2013-11-24 22:31 ` Mark Knecht
2013-11-25 2:14 ` Russell Coker
2013-11-25 9:20 ` David Brown
2013-11-21 8:08 ` joystick
2013-11-22 0:30 ` Stan Hoeppner
2013-11-22 0:33 ` H. Peter Anvin
2013-11-22 0:45 ` David Brown
2013-11-21 9:07 ` David Brown
2013-11-21 9:54 ` Adam Goryachev
2013-11-21 10:32 ` David Brown
2013-11-22 8:12 ` Russell Coker
2013-11-25 18:23 ` Pasi Kärkkäinen
2013-11-22 8:13 ` Stan Hoeppner
2013-11-22 13:15 ` David Brown
2013-11-22 16:07 ` Stan Hoeppner
2013-11-22 22:59 ` NeilBrown
2013-11-23 17:39 ` David Brown
2013-11-22 16:50 ` Mark Knecht
2013-11-22 19:51 ` Duncan
2013-11-22 8:38 ` Stan Hoeppner
2013-11-22 13:24 ` David Brown
2013-11-28 7:16 ` Stan Hoeppner
2013-11-28 7:36 ` Russell Coker
2013-11-28 9:56 ` David Brown
2013-11-30 7:32 ` Alex Elsayed
2013-12-01 15:37 ` Stan Hoeppner
2013-11-22 14:19 ` David Taylor [this message]
2013-11-21 19:56 ` Piergiorgio Sartor
2013-11-19 18:12 ` Piergiorgio Sartor
2013-11-20 10:44 ` David Brown
2013-11-20 21:59 ` Piergiorgio Sartor
2013-11-21 10:13 ` David Brown
2013-11-21 17:37 ` Goffredo Baroncelli
2013-11-21 20:05 ` Piergiorgio Sartor
2013-11-21 20:31 ` David Brown
2013-11-21 20:52 ` Piergiorgio Sartor
2013-11-22 0:32 ` David Brown
2013-11-22 20:32 ` Piergiorgio Sartor
2013-11-26 18:10 ` joystick
2013-11-20 21:38 ` Andrea Mazzoleni
2013-11-20 22:29 ` Piergiorgio Sartor
2013-11-23 7:55 ` Andrea Mazzoleni
2013-11-23 22:10 ` Piergiorgio Sartor
2013-11-24 9:39 ` Andrea Mazzoleni
-- strict thread matches above, loose matches on Subject: below --
2013-12-01 17:53 Richard Scobie
2013-12-02 4:30 ` Stan Hoeppner
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