[Box Backup-dev] Re: Learning from ZFS (fwd)

[Martin Ebourne]

Wout Mertens <wmertens at cisco.com> wrote:
> On 09 May 2007, at 18:25, Martin Ebourne wrote:
>
>> On Wed, 2007-05-09 at 16:58 +0200, Wout Mertens wrote:
>>
>>> 4. One thing that would really rock if extra code were added that
>>> only stores blocks with the same checksum once. ZFS currently doesn't
>>> have that, but I think it's technically feasible to do something like
>>> that.
>>
>> Er no, that wouldn't rock at all!
>
> Care to elaborate?

Well obviously given two arbitrary blocks that have the same checksum  
(or sha hash or whatever), it's very unlikely that the blocks are  
actually the same. It's pretty important for a backup system to give  
you back the actual data you stored, not just some data that happens  
to have the same checksum!

Cheers,

Martin.