From: Giovanni Tessore <giotex@texsoft.it>
To: Asdo <asdo@shiftmail.org>
Cc: linux-raid@vger.kernel.org
Subject: Re: Read errors on raid5 ignored, array still clean .. then disaster !!
Date: Sat, 30 Jan 2010 23:20:49 +0100 [thread overview]
Message-ID: <4B64B0C1.1040503@texsoft.it> (raw)
In-Reply-To: <4B64A779.6070809@shiftmail.org>
> RAID-5 unfortunately is inherently insecure, here is why:
> If one drive gets kicked, MD starts recovering to a spare.
> At that point any single read error during the regeneration (that's a
> scrub) will fail the array.
> This is a problem that cannot be overcome in theory.
Yes, I was just getting the same conclusion :-(
Suppose you have 2Tb mainstream disks, with a read error ratio of 1
sector each 1E+14 bits = 1.25E+13 bytes.
It means that you likely get an error every 6.25 times you read the
whole disk!
So in case of failure of a disk, you have 1 possibility over 6 to fail
the array during recostruction.
Simply unacceptable!
I looked at specs of some enterprise disks, and the read error ratio for
them is 1 sector each 1E+15 or each 1E+16. Better but still risky.
Ok.. I'll definitely move to raid-6.
Also raid-1 with less than 3 disks becomes useless the same way :-(
Idem for raid-10 ...wow
Well, these two threads on read errors came out as kinda instructive ...
doh!!
Regards
--
Cordiali saluti.
Yours faithfully.
Giovanni Tessore
next prev parent reply other threads:[~2010-01-30 22:20 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-26 22:28 Read errors on raid5 ignored, array still clean .. then disaster !! Giovanni Tessore
2010-01-27 7:41 ` Luca Berra
2010-01-27 9:01 ` Goswin von Brederlow
2010-01-29 10:48 ` Neil Brown
2010-01-29 11:58 ` Goswin von Brederlow
2010-01-29 19:14 ` Giovanni Tessore
2010-01-30 7:58 ` Luca Berra
2010-01-30 15:52 ` Giovanni Tessore
2010-01-30 7:54 ` Luca Berra
2010-01-30 10:55 ` Giovanni Tessore
2010-01-30 18:44 ` Giovanni Tessore
2010-01-30 21:41 ` Asdo
2010-01-30 22:20 ` Giovanni Tessore [this message]
2010-01-31 1:23 ` Roger Heflin
2010-01-31 10:45 ` Giovanni Tessore
2010-01-31 14:08 ` Roger Heflin
2010-01-31 14:31 ` Asdo
2010-02-01 10:56 ` Giovanni Tessore
2010-02-01 12:45 ` Asdo
2010-02-01 15:11 ` Giovanni Tessore
2010-02-01 13:27 ` Luca Berra
2010-02-01 15:51 ` Giovanni Tessore
2010-01-27 9:01 ` Asdo
2010-01-27 10:09 ` Giovanni Tessore
2010-01-27 10:50 ` Asdo
2010-01-27 15:06 ` Goswin von Brederlow
2010-01-27 16:15 ` Giovanni Tessore
2010-01-27 19:33 ` Richard Scobie
-- strict thread matches above, loose matches on Subject: below --
2010-01-27 9:56 Giovanni Tessore
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