1. A computer system, comprising: a memory; a storage medium storing a plurality of data items at respective addresses; a cache device also storing the plurality of data items at corresponding addresses and cache metadata providing a mapping between the address on the storage medium and the corresponding address on the cache device at which each data item is stored, the cache metadata being stored in a hierarchical data structure comprising a plurality of hierarchy levels; at least one processor programmed to: upon initiating a reboot of the computer, load only a subset of the plurality of hierarchy levels to the memory; and verify that a first data item of the plurality of data items was not modified after storage of the first data item in the cache device.