Re: RAID 1 not fixing up sector errors?

[Roman Mamedov <rm@romanrm.net>]

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On Thu, 14 Apr 2016 16:03:59 +0300
Dag Nygren <dag@newtech.fi> wrote:

> Hi!
> 
> Have set up a RAID1 here for temporary storage of some backup files.
> As I am using Seagate barracudas I am prepared for sector errors :-).
> that's why I am using RAID1.
> 
> Anyway I do get those occasional "Pending Reallocate" with
> the appropriate corresponding
> Unrecovered read error - auto reallocate failed
> in the log.
> 
> A resync of the array will rewrite the failing sector 
> and the drive seems to reallocate it and all is fine again .
> 
> But I was expecting the MD layer to try to fixup that sector
> automatically by using the data from the other drive ??
> 
> Is there something I need to explicitly enable?
> Or am I expecting too much ;-)

I have seen this behavior too. The only somewhat logical explanation that I
have, is that some drives are only able to remap bad sectors if a larger area
around the sector is overwritten, and not just the sector itself. But this is
not scientific or verified.

-- 
With respect,
Roman

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