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--- Robert Raschke <> wrote:

> > For how big a filesystem? If you have enough
> blocks, the probability
> > of a collision will be 1.
> Hmm, quoting
> in a
> bit
> more detail, says that for 1 exabyte stored in 8K
> blocks using a 160
> bit Sha1 hash for a block, the collision probability
> is less than 10^-20 :
> 	Are the 160 bit hash values generated by Sha1 large
> enough to
> 	ensure the fingerprint of every block is unique? 
> Assuming
> 	random hash values with a uniform distribution,

Unfortunately, it is impossible in general to know
whether whether the assumption of randomness and
uniformity of the has code is correct. Thus, relying
on that assumption may be hazardous to your data.