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From: Stan Hoeppner <stan@hardwarefreak.com>
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: linux-raid@vger.kernel.org
Subject: Re: Suboptimal raid6 linear read speed
Date: Fri, 18 Jan 2013 02:31:19 -0600	[thread overview]
Message-ID: <50F90857.3010305@hardwarefreak.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1301171648260.12098@uplift.swm.pp.se>

On 1/17/2013 9:51 AM, Mikael Abrahamsson wrote:

> The probability of getting struck by lightning is a lot less than being
> struck by a read error when rebuilding from the only remaining mirror
> when one drive failed and you've replaced it.

The probability of a URE during rebuild increases with the number and
size of the source drives being read to rebuild the failed drive.  Thus
the probability of encountering a URE in the 1:1 drive scenario is
extremely low, close to zero if you believe manufacturer specs.

> <http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162>
> is applicable to RAID1 and RAID10 as well as RAID5.

In Robin's example we're reading 12TB of sectors from 6 drives to
complete the rebuild of one failed drive, so the overall probably of a
URE is less than that of a single drive.  With RAID1/10 we're only
reading 2TB, well below the URE rates for single drives.

So, no, the "URE scare" being propagated these days doesn't affect
RAID1/10.  If/when individual drive capacities exceed 10TB in the
future, and if at that time the URE rates per drive do not improve,
-then- this phenomenon will affect RAID1/10.  But it does not currently
with today's drives.

-- 
Stan


  reply	other threads:[~2013-01-18  8:31 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-15 12:33 Suboptimal raid6 linear read speed Peter Rabbitson
2013-01-15 12:45 ` Mikael Abrahamsson
2013-01-15 12:56   ` Peter Rabbitson
2013-01-15 16:13     ` Mikael Abrahamsson
2013-01-15 12:49 ` Phil Turmel
2013-01-15 12:55   ` Peter Rabbitson
2013-01-15 17:09     ` Charles Polisher
2013-01-15 19:57       ` keld
2013-01-16  4:43         ` Charles Polisher
2013-01-16  6:37           ` Tommy Apel Hansen
2013-01-16  9:36           ` keld
2013-01-16 16:09             ` Charles Polisher
2013-01-16 20:40               ` EJ Vincent
2013-01-15 23:17     ` Phil Turmel
2013-01-16  2:48     ` Stan Hoeppner
2013-01-16  2:58       ` Peter Rabbitson
2013-01-16 20:29         ` Stan Hoeppner
2013-01-16 21:20           ` Roy Sigurd Karlsbakk
2013-01-17 15:51           ` Mikael Abrahamsson
2013-01-18  8:31             ` Stan Hoeppner [this message]
2013-01-18  9:18               ` Mikael Abrahamsson
2013-01-18 22:56                 ` Stan Hoeppner
2013-01-19  7:43                   ` Mikael Abrahamsson
2013-01-19 22:48                     ` Stan Hoeppner
2013-01-19 23:51                       ` Maarten
2013-01-20  0:16                         ` Chris Murphy
2013-01-20  0:49                           ` Maarten
2013-01-20  1:37                             ` Phil Turmel
2013-01-20  9:44                             ` Chris Murphy
2013-01-20  6:26                           ` Mikael Abrahamsson
2013-01-20  9:39                             ` Chris Murphy
2013-01-20 16:55                               ` Mikael Abrahamsson
2013-01-20 17:15                                 ` Chris Murphy
2013-01-20 17:17                                   ` Mikael Abrahamsson
2013-01-20 17:20                                     ` Chris Murphy
2013-01-19 23:53                       ` Phil Turmel
2013-01-20  9:04                     ` Wolfgang Denk
2013-01-20 19:28                     ` Peter Grandi
2013-01-20 21:09                       ` Mikael Abrahamsson
2013-01-20 21:50                         ` Peter Grandi
2013-01-21  5:24                           ` Mikael Abrahamsson
2013-01-21 14:40                       ` Peter Rabbitson
2013-01-21 20:32                         ` Peter Grandi
2013-01-21 20:55                           ` Peter Grandi
2013-01-21 22:00                         ` Peter Grandi
2013-01-19 13:21                   ` Roy Sigurd Karlsbakk

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