Re: [dm-devel] [PATCH 0/4] dm verity: add support for error correction

From: Zdenek Kabelac
Date: Fri Nov 06 2015 - 16:05:32 EST

Dne 6.11.2015 v 21:27 Sami Tolvanen napsal(a):
On Fri, Nov 06, 2015 at 08:20:15PM +0100, Zdenek Kabelac wrote:
i.e. you have 1G of space - you want to give 250MB as 'redundancy' -
so create 4 partition....

well data safety has it's price - user should choose what he prefers
- more games and videos or more safety...

We cannot afford to set aside 25% of read-only partition space for
redundancy on mobile devices, and would rather not impact performance
any more than dm-verity already does. With error correction we have
0.8% space overhead in our use case and no performance degradation if
the partition is not corrupted.

I'm probably missing here some hw knowledge here - but if you loose
a flash block of some size - then you typically get 'error' for
all bytes the sector/block.

So how do you want to correctly 'restore' missing full sectors with just 0.8% data overhead ??

Or is the device which fails to correct block returning something 'still usable' (since e.g. SATA disk certainly not)


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