Techniques relating to data deduplication at the file system level are disclosed. A system may include a block cache configured to store data blocks indicated as being shared by multiple files. The system may be coupled to a storage configured to permanently store data for the multiple files. The computer system may receive a file request, and, upon determining that the file request includes shared data, the computer system may service the request wholly or in part using the block cache. When multiple requests including multiple file identifiers (but referring to the same underlying shared data) are received, a shared (common) file identifier may be used in looking up data for the multiple requests, reducing block cache storage, and improving block cache performance and overall system operation.