[tahoe-dev] Recombinant Hashes
zooko at zooko.com
Fri Feb 12 05:55:56 UTC 2010
On Thursday, 2010-02-11, at 22:31 , David-Sarah Hopwood wrote:
> According to this ticket: <http://allmydata.org/trac/tahoe/ticket/
> 678>, the FEC code that Tahoe uses also has the property that the
> content of some initial subset of shares does not depend on the
> total number of shares. If that's correct, it's not clear to me why
> it it's not also classified as a fountain code, although I've never
> heard of Reed-Solomon codes referred to as fountain codes.
Perhaps because there is a fixed upper limit on how many unique
shares we can generate. The erasure code library that Tahoe-LAFS uses
-- zfec -- maxes out at 256 shares. The library from which zfec was
derived also included a variant that maxed out at 65536 but encoding
and decoding would be slower.
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