From: Maarten <maarten@ultratux.net>
To: linux-raid@vger.kernel.org
Subject: Re: Suboptimal raid6 linear read speed
Date: Sun, 20 Jan 2013 00:51:33 +0100 [thread overview]
Message-ID: <50FB3185.7060009@ultratux.net> (raw)
In-Reply-To: <50FB22D8.5000803@hardwarefreak.com>
On 01/19/13 23:48, Stan Hoeppner wrote:
> On 1/19/2013 1:43 AM, Mikael Abrahamsson wrote:
>
>> With a BER of 10^-14 you have a 16% risk of getting URE when reading an
>> entire 2TB drive.
> On 1/19/2013 7:21 AM, Roy Sigurd Karlsbakk wrote:
>
>> ok, perhaps, maybe, but then it's 17% chance of losing data after a
>> mirror or raid-5 rebuild with 2TB drives...
> Where are you guys coming up with this 16-17% chance of URE on any
> single full read of this 2TB, 10E14 drive? The URE rate here is 1 bit
> for every 12.5 trillion bytes. Thus, statistically, one must read this
> drive more than 6 times to encounter a URE. Given that, how is any
> single full read between the 1st and the 6th going to have a 16-17%
> chance of encountering a URE for that one full read? That doesn't make
> sense.
Sorry but now I have to speak up too. Of course that 16-17% figure is
right! Did you miss out on math classes ? It is all statistics. There is
a chance of '1.0' to get one URE reading 12.5 TB. That URE may be
encountered at the very start of the first TB, or it may not come at
all, because that is how statistics work. But *on*average*, you'll get
1.0 URE per 12.5 TB, ergo, 0.16 per 2.0 TB. Basic simple math... jeez.
Can we now give it a rest? Or do I need to unsubscribe ?
Cheers,
Maarten
next prev parent reply other threads:[~2013-01-19 23:51 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
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 [this message]
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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