RE: feature suggestion to handle read errors during re-sync of raid5

["Guy Watkins" <linux-raid@watkins-home.com>]

I have always read that drives remap on failed write.
But have not read anything new in 2+ years.

} -----Original Message-----
} From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
} owner@vger.kernel.org] On Behalf Of Mikael Abrahamsson
} Sent: Monday, February 01, 2010 2:16 AM
} To: Linux RAID
} Subject: Re: feature suggestion to handle read errors during re-sync of
} raid5
} 
} On Sun, 31 Jan 2010, Roger Heflin wrote:
} 
} > Bit errors seem more likely the longer a sector has set since being
} > written. I would be not expect to see errors if you read the entire
} > disk, and then reread it 1x a day for a year, but if you read the disk
} > once, let it sit spinning for a year without any reads and read it
} > again, this will almost certainly get a read error.  When you keep
} > rereading it, when the bits start to go bad the disk should move it long
} > before data loss happens, but if you only read it 1x a year, it is
} > likely that when you find the data bad there will be too many bad bits,
} > beyond being able to correct it.
} 
} Are you sure that drives today remap like that (if it tries to read it and
} only succeeds on the 5th try, it'll reallocate the sector)?
} 
} Looking at "reallocated sectors" on my drives, I've never seen this
} happen. That SMART parameter has never increased unless I had a hard UNC
} and re-wrote the sector (and a lot of the times, not even that).
} 
} --
} Mikael Abrahamsson    email: swmike@swm.pp.se
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