US Patent 10061775 Scalable and persistent L2 adaptive replacement cache

A method, system and a computer program product for managing file system memory includes a module configured to implement a separate replacement policy and a separate index for a persistent second level adaptive replacement cache (L2ARC) logically part of a first level ARC. The system also includes a module configured to cluster compressed chunks of data on multiple physical devices via aligning the clusters of data chunks on a byte boundary basis on each of the devices. The method additionally includes a module configured to create a storage pool allocator (SPA) to track the compressed and packed chunks on the multiple devices via an attached active page and attached multiple closed pages. The method further includes re-adding an evicted data from the L2ARC to an active page to be written again thereto based on a configurable threshold number of hits to data in the L2ARC via an L2ARC hit counter.