Re: [RFE] Please, add optional RAID1 feature (= chunk checksums) to make it more robust

[keld@keldix.com]

On Wed, Jul 18, 2012 at 07:01:48AM -0400, Jaromir Capik wrote:
> Hello.
> 
> I'd like to ask you to implement the following ...
> 
> The current RAID1 solution is not robust enough to protect the data
> against random data corruptions. Such corruptions usually happen
> when an unreadable sector is found by the drive's electronics
> and when the drive's trying to reallocate the sector to the spare area.
> There's no guarantee that the reallocated data will always match
> the original stored data since the drive sometimes can't read the data
> correctly even with several retries. That unfortunately completely masks
> the issue, because the sector can be read by the OS without problems
> even if it doesn't contain correct data. Would it be possible
> to implement chunk checksums to avoid such data corruptions?
> If a corrupted chunk is encountered, it would be taken from the second
> drive and immediately synced back. This would have a small performance
> and capacity impact (1 sector per chunk to minimize performance impact
> caused by unaligned granularity = 0.78% of the capacity with 64k chunks).
> 
> Please, let me know if you find my request reasonable or not.

I believe alternative to that is implemented via the Linux RAID MD badblock feature.

best regards
keld