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Thomas Waldmann
61b1b83059
fastcdc is ~1.3x faster than buzhash/buzhash64 at the same deduplication and (with normalized chunking) a tighter chunk size distribution. It is also the better choice security-wise: its Gear table is derived from secret key material, while the "buzhash" chunker only XORs a 32bit seed into its table - so chunk cut points are much harder to predict without the key (resistance against chunk-size fingerprinting attacks). Both places using a chunker are switched: - CHUNKER_PARAMS (file content data): fastcdc,19,23,21,2 - ITEMS_CHUNKER_PARAMS (item metadata stream): fastcdc,15,19,17,2 The metadata stream chunker was still using the 32bit seeded buzhash, so this also closes that gap. Also rename CHUNKER64_PARAMS -> BUZHASH64_PARAMS and add BUZHASH_PARAMS, so the per-algorithm defaults are named consistently and CHUNKER_PARAMS unambiguously means "the default chunker". This is intentionally done during the beta phase so it gets plenty of practical testing before borg2 is released for production.