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SubjectRe: Transparent compression in the FS
On Wed, Oct 15, 2003 at 11:13:27AM -0400, Jeff Garzik wrote:
> Josh and others should take a look at Plan9's venti file storage method
> -- archival storage is a series of unordered blocks, all of which are
> indexed by the sha1 hash of their contents. This magically coalesces
> all duplicate blocks by its very nature, including the loooooong runs of
> zeroes that you'll find in many filesystems. I bet savings on "all
> bytes in this block are zero" are worth a bunch right there.

The only problem with this is that you can get false positives. Val Hensen
recently wrote a paper about this. It's really unlikely that you get false
positives but it can happen and it has happened in the field.
Larry McVoy lm at
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