From: Michael Evans <mjevans1983@gmail.com>
To: dong wu <dongwucs@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: when read error ,where do we rewrite?
Date: Thu, 7 Jan 2010 22:35:29 -0800 [thread overview]
Message-ID: <4877c76c1001072235m2790209exe0601e410889d52f@mail.gmail.com> (raw)
In-Reply-To: <6c394cc31001072059t2669afa8l5fed42ff77b3c134@mail.gmail.com>
On Thu, Jan 7, 2010 at 8:59 PM, dong wu <dongwucs@gmail.com> wrote:
> In the source code of raid5,when write error,it faulty the disk,not remap
> the block. why do it use "remap the block"?
>
> 2010/1/8, dong wu <dongwucs@gmail.com>:
>> If it is written to the same block,will it read error again?
>> when read error,the low-level attempts a write and remap the block if
>> the write fails.
>> where does it remap?
>> Is there any spare block in the disk for remap when read or write error occurs?
>>
>> 2010/1/7, Robin Hill <robin@robinhill.me.uk>:
>> > On Thu Jan 07, 2010 at 08:41:20PM +0800, dong wu wrote:
>> >
>> > > when read error and can rewrite,where do we rewrite?
>> > > It can't be rewrited to the old block.
>> > > It should be rewrite to other place,where can we find the 'other place'?
>> > > In the source code,I don't find the place that should be rewrited to.
>> > >
>> > It's rewritten to the same block - it's up to the low-level device (the
>> > disk) to attempt a write and transparently remap the block if the write
>> > fails.
>> >
>> > Cheers,
>> > Robin
>> > --
>> > ___
>> > ( ' } | Robin Hill <robin@robinhill.me.uk> |
>> > / / ) | Little Jim says .... |
>> > // !! | "He fallen in de water !!"
>> >
>> >
>>
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Modern mass storage devices provide an /abstraction/ of a linear
storage device which needn't actually be so. On most of them data
plus some extra parity for recovery are stored; if the drive has
unusual trouble reading the data back, it will try to get a good
read/repair and then use another, spare (reserved), area on the device
in place of the one that 'went bad'. This is actually a major problem
for cryptographic/security concerns, and is one possible metric in
S.M.A.R.T. data that can indicate a failing drive.
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next prev parent reply other threads:[~2010-01-08 6:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-07 12:41 when read error ,where do we rewrite? dong wu
2010-01-07 13:18 ` Robin Hill
2010-01-08 4:54 ` dong wu
2010-01-08 4:59 ` dong wu
2010-01-08 6:35 ` Michael Evans [this message]
2010-01-08 10:03 ` Robin Hill
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