US Patent 8032707 Managing cache data and metadata

Embodiments of the invention provide techniques for managing cache metadata providing a mapping between addresses on a storage medium (e.g., disk storage) and corresponding addresses on a cache device at data items are stored. In some embodiments, cache metadata may be stored in a hierarchical data structure comprising a plurality of hierarchy levels. Only a subset of the plurality of hierarchy levels may be loaded to memory, thereby reducing the memory “footprint” of cache metadata and expediting the process of restoring the cache metadata during startup operations. Startup may be further expedited by using cache metadata to perform operations associated with reboot. Thereafter, as requests to read data items on the storage medium are processed using cache metadata to identify addresses at which the data items are stored in cache, the identified addresses may be stored in memory. When the computer is later shut down, instead of having to transfer the entirety of the cache metadata from memory to storage, only the subset of the plurality of hierarchy levels and/or the identified addresses previously loaded to memory may be transferred (e.g., to the cache device), thereby expediting the shutdown of the computer.