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Steve Heller wrote:

On Thu, 10 May 2007 02:02:04 -0400, Dave Dodge
<> wrote:

This design requires that every unique block of data, in
every file in the filesystem, has a unique hash value.  A
collision results in data loss.

   "Using the Sha1 hash function, the probability of a
   collision is less than 10^-20. Such a scenario seems
   sufficiently unlikely that we ignore it [...]"

For how big a filesystem? If you have enough blocks, the
probability of a collision will be 1.

Follow the link; the number quoted is for

[A] system that contains an exabyte (10^18 bytes) [a
million terabytes] stored as 8 Kbyte blocks (~10^14