International Business Machines Corporation

Shaunchi Ong

Windsor Hsu

John Davis Palmer

A method for reducing data loss and unavailability by integrating multiple levels of a storage hierarchy is provided. The method includes receiving a read request. In addition, the method includes recognizing a data failure in response to the read request. The method further includes locating an alternate source of the data to be read in response to recognizing the data failure. The alternate source includes data cached at devices in the storage hierarchy, data in a backup system, and cumulative changes to the data since the last backup. Moreover, the method includes responding to the read request with data from the alternate source.

Reducing data loss and unavailability by integrating multiple levels of a storage hierarchy

The invention provides a method for ensuring that data stored on rewritable storage is immutable. The method includes initializing selected user-addressable blocks of storage to a writable state. In addition, the method includes accepting data to be stored in specified user-addressable blocks. Also, the method includes determining if the specified block(s) is writable. Also, the method includes storing the accepted data to the rewritable storage. Moreover, the method includes setting the state of the specified block(s) to non-writable. In one embodiment, the writable/non-writable state associated with each block is encoded and stored in the contents of the corresponding block. In another embodiment, the steps of determining whether the specified block(s) is writable, storing the accepted data to the rewritable storage, and setting the state of the specified block(s) to non-writable, are integrated and indivisible.

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San Jose, CA, United States of America

Shaunchi Ong