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Steve Heller wrote:
On Thu, 10 May 2007 02:02:04 -0400, Dave Dodge <dododge@dododge.net> 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 [...]" http://plan9.bell-labs.com/sys/doc/venti.htmlFor 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 blocks).
-- Aaron http://arundelo.com/