Abstract: Described is a technology by which a secondary nonvolatile storage (e.g., a flash memory device) maintains a copy of the changes made to a hard drive after a data backup operation. The backup changes are combinable with backed up data to recreate a hard drive state, whereby changes after the last backup are not lost, e.g., if the hard drive fails. The backup change data may maintain the changes at the block (e.g., allocation unit) level corresponding to hard drive blocks, or at the file level, corresponding to files or parts of files on the hard drive. The backup changes may be filtered, so that only certain data (e.g., user data) are maintained as backup change data. Read requests can be satisfied by reading data from the backup change data, or from a performance (e.g., disk) cache that may also reside on the nonvolatile storage.

Abstract: A method and system for keeping endpoints such as speakers and displays synchronized via feedback based on the actual output of the endpoints. A source of audiovisual content transmits corresponding digital data to one or more endpoints, such as over a home network, where it may be buffered and/or decoded for playback. Microphones or the like sense actual (post-buffering/decoding) output from one or more endpoints and feed it back to a synchronization mechanism. The synchronization mechanism employs pattern matching or similar techniques to determine whether and how to adjust the timing of endpoints to synchronize their actual outputs. Synchronization may be accomplished by controllably delaying transmission and/or other processing, by controllably changing the rate of advancing in a buffer, and/or by jumping ahead in a buffer. The synchronization mechanism may adjust multiple endpoints, e.g., when limited buffer size limits the amount of adjustment a single device can provide.