Patent attributes
A disk drive that includes nonvolatile memory for use when the disk drive is in standby mode also uses the nonvolatile memory, together with a volatile memory, as a cache when the disk drive is in both standby and non-standby mode. Each of the data blocks stored on the disks is also stored in a cache line of either the volatile memory or the nonvolatile memory. Each cache line in both the volatile and nonvolatile memory stores one or more data blocks and an associated tag. The tag contains at least a portion of the logical block address that corresponds to the data block that is stored in the cache line. The volatile memory also has locations allocated to store tags that “shadow” the tags in the nonvolatile memory. By searching the shadow tags in the faster volatile memory, it can be determined if a data block is in the nonvolatile memory without searching the slower nonvolatile memory.
