Yes. Depending on how the claim languages are phrased, patents on the same idea can be approved. For reclaiming deleted blocks, I just had a garbage collectio

Yes. Depending on how the claim languages are phrased, patents on the same idea can be approved. For reclaiming deleted blocks, I just had a garbage collection phase to run from time to time. Like you've mentioned on refcount, I've considered it but it amplified writes 2X~3X and worse they were random access writes. Garbage collection was not so bad since it's only going through the virtual file control blocks containing the content-address-hash. The storage layout was: file block -> virtual file control block -> dedup-data-block. The virtual file control block contained the dedup block hash entries where one control block hosted N file blocks. GC only needed to scan the control blocks to find out which dedup-data-blocks were in use. Freed dedup-data-blocks remained in place and were linked to the free list; the first couple bytes of the free block were cooped to store the pointer to the next free block. At the end, brand new file write performance degraded about 10% compared to normal file write, which I considered acceptable. M block writes -> M dedup block writes + M/N control block writes + M/K db index updates, where N was the number of hash entries hosted in the control block and K is the number of hashes stored in one db index page. Repeated file writes were much faster due to deduplication.