Preparing data for deduplication including: generating, by a storage system for a compressed data block, a padded compressed data block by padding the compressed data block to conform to a fixed block size, wherein the fixed block size is greater than a size of the compressed data block; storing, in the storage system, the padded compressed data block beginning at a block boundary of a storage device in the storage system; and performing block-based deduplication on the storage system, wherein the block-based deduplication determines whether the padded compressed data block matches one or more other padded compressed data blocks stored in the storage system.