[Ocfs2-devel] [PATCH 0/18] ocfs2: Add metadata ECC - almost there.

[Andi Kleen]

On Wed, Dec 10, 2008 at 10:15:52AM -0800, Joel Becker wrote:
> On Wed, Dec 10, 2008 at 01:54:51PM +0100, Andi Kleen wrote:
> > Joel Becker <joel.becker at oracle.com> writes:
> > 
> > > These patches add the metadata ECC code to ocfs2.  They have one
> > > limitation - they do not ECC directory blocks yet.  However, that will
> > > only take a simple insertion of the dirblock trailer.  With xattr ECC
> > > completed, the patches are approaching a final form and are ready for
> > > initial review.  They are atop my xattr-buckets-2 branch.
> > 
> > Could you please expand a bit why you chose ECC over more standard CRCs?
> > 
> > My assumption would be normally that if there is disk corruption it won't
> > be single flipped bits, but more large scale corruption. Do you have
> > data/experiences on the contrary?
> 
> 	If you look at our block_check structure, you'll see that it
> uses crc32c for the overall block, and then the ECC can attempt to
> correct a single bit if the crc fails.

Understood. But why did you decide you need ECC?

-Andi

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ak at linux.intel.com