Not really. ZFS dedup is just brain-dead stupid. Rabin-Karp chunking plus spatial locality / opportunistic dedup allow you to gracefully scale down: you keep a

Not really. ZFS dedup is just brain-dead stupid. Rabin-Karp chunking plus spatial locality / opportunistic dedup allow you to gracefully scale down: you keep a complete table of successfully deduped blocks, plus a small fraction of other blocks, like e.g. smallest 1% of hashes, first blocks in files and final blocks in files. If you have a 12 MB (100 blocks) stretch that matches, you have 63% (1-1/e) chance of discovering one of these blocks as a match, and then use spatial locality to dedup adjacent blocks (duplicate blocks tend to come in bunches).