Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication

[ronnie sahlberg]

On Wed, Jan 2, 2013 at 11:18 AM, Troy Benjegerdes <address@hidden> wrote:
> If you do get a hash collision, it's a rather exceptional event, so I'd
> say every effort should be made to log the event and the data that created
> it in multiple places.
>
> There are three questions I'd ask on a hash collision:
>
> 1) was it the data?
> 2) was it the hardware?
> 3) was it a software bug?

Yes, that is probably good too, and saving off the old and new block
content that collided.

Unless you are checksumming the blocks, I suspect that the most common
reason for "collisions" would just be cases where the original block
was corrupted/changed on disk and you dont detect it and then when you
re-write an identical one the blocks no longer match and thus you get
a false collision.