Abstract: Described herein are exemplary storage network architectures and methods for block size allocation in copy operations. A copy operation from a first storage cell to a second storage cell is initiated. The copy operation initially utilizes a first write block size. The write block size is changed to utilize a second write block size, different from the first write block size, and a performance parameter is measured at the second write block size. The second write block size is maintained if the performance parameter exceeds a threshold.

Abstract: A disaster recovery system with sequenced cascaded resynchronization comprises a plurality of data centers and a distributed control system. The individual data centers comprise a communication interface, a data storage, and a controller. The distributed control system is distributed and executable in the controllers of the plurality of data centers, and is capable of coordinating operations via the communication interfaces of the plurality of data centers to resynchronize a plurality of communication links between data center pairs of the plurality of data centers. The communication links including at least one synchronous link and at least one asynchronous link.

Abstract: A method and system for fairly distributing servicing of I/O requests by a storage device among remote computers that contract for a specified maximum rate of I/O request servicing by the storage device. The remote computers also specify whether the storage device should employ a simple throttling technique or a sliding window throttling technique to limit the rate of I/O request servicing to the contracted-for rate of I/O request servicing. In the simple throttling technique, the storage device services up to some maximum number of I/O requests per unit time for the remote computer, regardless of the overall time-averaged rate of I/O request servicing provided to the remote computer. In the sliding window throttling technique, the storage device maintains an approximate, periodically re-calculated instantaneous rate of I/O request servicing calculated based on recent I/O request servicing by the storage device on behalf of the remote computer.

Abstract: A method and system for employing fast, but easily corrupted mass storage for reliably backing up objects, such as files and database. In a LUN-based mass storage device, a timestamp is updated or a counter incremented after each I/O operation directed to the LUN that may alter data stored on the LUN. An entity may retrieve from the mass storage and save a current timestamp or current counter for a LUN at the time a backup is made to the LUN. Later, prior to using the backup in a restore operation, the entity may re-retrieve the timestamp or counter for the LUN and compare it to the saved timestamp or counter in order to determine whether or not the backup has been potentially altered.

Abstract: A disaster recovery system with sequenced cascaded resynchronization comprises a plurality of data centers and a distributed control system. The individual data centers comprise a communication interface, a data storage, and a controller. The distributed control system is distributed and executable in the controllers of the plurality of data centers, and is capable of coordinating operations via the communication interfaces of the plurality of data centers to resynchronize a plurality of communication links between data center pairs of the plurality of data centers. The communication links including at least one synchronous link and at least one asynchronous link.

Abstract: A method and system for employing fast, but easily corrupted mass storage for reliably backing up objects, such as files and databases. In a LUN-based mass storage device, a system or application may request and receive a lock on a particular LUN prior to storing a backup object on the LUN. The system or application may later request lock information for the LUN in order to decide whether or not the backup object can be reliably used for a restore operation. If the system or application continues to hold a lock on the LUN, then the backup object is reliable.

Abstract: A method and system for providing to a human user or high-level application program a functional interface for translating the names of logical objects into physical mappings of logical objects to physical storage locations within a mass storage device and for allowings a human user or high-level application program to request that two logical objects be physically separated within a mass storage device so that a single failure cannot corrupt both logical objects, the physical separation optionally monitored over time to guarantee that logical objects are not subsequently remapped in a way that results in partial or full overlap.

Abstract: An apparatus, method, computer readable medium and logical device have been created for storing essentially only modified or changed information from one of a pair of mirrored storage devices. In one exemplary embodiment, essentially only tracks of information from a primary volume of a mirrored pair of mirrored storage units, which have been modified since creation of the mirror, need be stored. In another exemplary embodiment, essentially only tracks of information from a primary volume of a mirrored pair of mirrored storage units, which have been modified since a last resynchronization, need be stored. In yet another exemplary embodiment, essentially only tracks of information from a primary volume of a mirrored pair of mirrored storage units, which have been modified since a last command, need be stored. By storing actual information which was modified and by storing essentially only information which was modified, a small amount of actual information need be stored.