Re: Transparent compression in the FS

[Christopher Li]

> The idea of this sort of block level hashing to allow
> sharing of identical blocks seems attractive but i wouldn't
> trust any design that did not accept as given that there
> would be false positives.  This means that a write would
> have to not only hash the block but then if there is a
> collision do a compare of the raw data.  Then you have to
> add the overhead of having lists of blocks that match a hash
> value and reference counts for each block itself.  Further,

Then write every data block will need to dirty at least 2 blocks.
And it also need to read back the original block if hash exist.
There must be some performance hit. 

Chris
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