From: Mirko Benz <mirko.benz@web.de>
To: Neil Brown <neilb@suse.de>
Cc: Linux RAID <linux-raid@vger.kernel.org>
Subject: Re: parity check for read?
Date: Wed, 04 Apr 2007 13:29:10 +0200 [thread overview]
Message-ID: <46138C06.5020903@web.de> (raw)
In-Reply-To: <17938.49705.840745.66635@notabene.brown>
Neil,
Exactly what I had in mind.
Some vendors claim they do parity checking for reads. Technically it
should be possible for Linux RAID as well but is not implemented – correct?
Reliability data for unrecoverable read errors:
- enterprise SAS drive (ST3300655SS): 1 in 10^16 bits transfered, ~ 1
error in 1,1 PB
- enterprise SATA drive (ST3500630NS): 1 in 10^14 bits transfered, ~ 1
error in 11 TB
For a single SATA drive @ 50 MB/s it take on average 2,7 days to
encounter an error.
For a large RAID with several drives this becomes much lower or am I
viewing this wrong?
Regards,
Mirko
Neil Brown schrieb:
> On Tuesday April 3, mirko.benz@web.de wrote:
>
>> Hi,
>>
>> Is parity calculation and validation for read operations supported?
>>
>
> I guess what you are asking is:
>
> With raid5, I would like the drive to handle a read request by
> reading all the blocks in the stripe and checking the parity. If
> the parity is correct, return the data blocks. If it is not, then
> fail the read request. Is that possible?
>
> No, it is not.
>
> If you are really asking something else, please be more specific.
>
> NeilBrown
>
>
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next prev parent reply other threads:[~2007-04-04 11:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-03 13:21 parity check for read? Mirko Benz
2007-04-03 21:07 ` Neil Brown
2007-04-04 11:29 ` Mirko Benz [this message]
2007-04-04 13:35 ` Ric Wheeler
2007-04-04 15:57 ` Dan Williams
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