Abstract: Provided are a method, system, and article of manufacture, wherein a controller receives a request from one of a plurality of hosts. The controller determines whether a primary storage control unit coupled to the controller is operational. A response is generated by accessing the primary storage control unit, in response to determining that the primary storage control unit is operational. The response is generated by accessing a secondary storage control unit, in response to determining that the primary storage control unit is not operational, wherein data is replicated synchronously from the primary storage control unit to the secondary storage control unit.

Abstract: A method of transmitting information from a primary storage control unit to a secondary storage control unit in an asynchronous data copying system. The method includes building multiple descriptor blocks for transmission from the primary storage control unit, and encrypting multiple payloads according to one of n encryption methods. In addition, the n encryption methods are associated with the primary storage control unit and n decryption keys relating to the n encryption methods are associated with the secondary storage control unit. An index to the n encryption keys is associated with the multiple descriptor blocks. The method further includes encrypting each of the payloads according to one of the n encryption methods and indicating, in the index associated with a selected descriptor block, which decryption key relates to the encryption method used for any payload associated with a select descriptor block.

Abstract: A method, apparatus, and article of manufacture containing instructions for processing multiple point-in-time consistent data sets. The method consists of creating multiple point-in-time data sets associated with a backup appliance which is associated with backup storage. Upon the transfer of a first update from a primary storage controller to the backup appliance, a determination is made whether the update affects data stored in the backup storage has been unchanged following the creation of the respective data sets. If the update does affect data which is unchanged following the creation of a data set, the current, non-updated data is read from the backup storage. A copy of the current, non-updated data thus read from the backup storage is stored in a storage location which can be one of the data sets or an independent memory location. In addition, pointers are associated with the remaining applicable data sets and directed to the copy at its storage location.

Abstract: An apparatus, system, and method are disclosed for reliably updating a data group in a data replication environment. The apparatus, system, and method reliably update the data group by receiving an updated data group sent from a first storage medium to a second storage medium, comparing the updated data group with a previous data group previously existing on the second storage medium and writing the updated data group to the second storage medium. The read-before-write and differencing method disclosed maintain reliability by storing multiple copies of changes made to the second storage medium during and after the write process.

Abstract: An apparatus, system, and method are disclosed for efficient creation of point-in-time versions of data using differencing in a read-before-write environment. Included in an embodiment of the invention are a receive module that receives a data block sent from a primary data storage system, a read module that reads a data block from a secondary data storage device into random access memory, the data block corresponding to the data block sent from the primary data storage system, a comparison module that compares the data block sent from the primary data storage system to the data block from the secondary data storage device and creates a differencing data file, a compression module that compresses the differencing data file and to create a compressed differencing data file, and a differencing storage module stores the compressed differencing data file in a differencing storage device.

Abstract: Provided are a method, system and program for prefetching data into cache. A prefetch command is processed that indicates at least one conditional statement and at least one block to prefetch from storage to cache in response to determining that the conditional statement is satisfied.

Abstract: A system, method and computer program product are provided to improve the efficiency of the transmission of consistency groups across multiple storage components by ensuring that volume transactions are evenly allocated among backup components. Each volume is initially assigned to a specified backup component. Once a color period begins, volume transactions are transmitted to the assigned backup component. Each backup component accumulates data transfer information for its assigned volumes throughout at least a portion of the color period and calculates a new volume assignment for the next color period. Before the start of the next color period, a captain storage controller transmits any new assignments to the backup components. During a next color period, the process is repeated using the new assignments.

Abstract: Disclosed is a technique for transferring data using multiple backup components. Responsibility for a portion of data is assigned to a first backup component. When a data update for the portion of data is received at the first backup component from a primary source, the data update is mirrored to a second backup component that is not assigned responsibility for the portion of data. Also disclosed is a technique for processing data updates with a group of backup components. It is determined that a new backup component is active. Near an end of a consistent transactions set formation period, responsibility for one or more portions of data are assigned to each backup component in the group and to the new backup component. During a next consistent transactions set formation period, data updates are processed with each backup component in the group and the new backup component. Moreover, disclosed is a technique for processing data updates with a group of backup components.

Abstract: A network component useful in tracking write activity by writing logs containing write address information is described. The tracking component may be used in networked systems employing data mirrors to record data block addresses written to a primary storage volume during the time a data mirror is unavailable. The tracking component can be available to any network originating node, and may therefore track write activity on multiple volumes. At the time a data mirror is reconstructed, the log written may be used to construct a list of block addresses pointing to locations on a primary storage volume wherein data differs from a secondary storage volume member of the mirror. The locations maybe copied from the primary to secondary storage volume to reconstruct the data mirror. The performance impact of the tracking component is minimal and a shared network resource is offered that increases fault tolerance in the event of backup device failures.

Abstract: Disclosed is a technique for data synchronization. A first identifier is determined for a portion of data at a first source. A second identifier is determined for a portion of corresponding data at a second source. The first and second identifiers are compared. When the first and second identifiers do not match, the portion of corresponding data at the second source is replaced with the portion of data at the first source.

Abstract: A method to select a captain control node from a plurality of interconnected control nodes is disclosed. The method provides by each of the plurality of control nodes a first signal to each of the other control nodes, and then receives by each of the plurality of control nodes, a response signal from each of the other control nodes. The method then calculates by each of the plurality of control nodes individual response times for each of the other control nodes, and determines by each control node its aggregate response time. The method then determines whether to select a captain control node using the aggregate response times. If the captain control node is selected using the aggregate response times, then the method then determines the minimum aggregate response time, and designates the control node having that minimum aggregate response time the captain control node.

Abstract: A method to adjust the data transfer rate for one of (N) primary backup appliances. The method forms by a first primary backup appliance at least one consistent transactions set. The first primary backup appliance receives the (n)th status signal, and the (n+1)th status signal from each of the other (N?1) primary backup appliances. The method calculates the (n)th effective bandwidth for each of the (N) primary backup appliances, the (n)th time to complete for each of the (N) primary backup appliances, and the (n)th effective aggregate bandwidth for all (N) primary appliances. If the (n)th time to complete for the first primary backup appliance is greater than the (n)th time to complete for each of the other (N?1) primary backup appliances, then the method provides at least one consistent transactions set from the first primary backup appliance to a first secondary backup appliance with no delay.

Abstract: Disclosed are a system, a method, and a computer program product to provide for the optimization of the output transfer load balance between the peer computers transferring data to one or more storage devices. The peer computers receive, organize and transfer the data to storage devices. The data set is composed of a plurality of data transfers. After an initial division of the data transfers between the two peers, each peer will have assigned responsibility for a number of data transfers. If the one of the peer computers completes offloading transactions earlier than the other peer, then the peer that is still transferring data will employ the other peer to execute a portion of the remaining data transfers. The operation of the system is symmetrical in that either peer may assist the other peer depending upon which peer has idle time.

Abstract: Disclosed are a system, a method, and a computer program product to optimize the overall latency of transferring data from peer computers to storage devices. The latency optimization occurs after a group of data is received and organized by the peer computers. The average amount of time to transfer data to each particular storage device from the peer computers is used to determine the assignment of data transfers between the peer computers. Each peer computer maintains continuously updated measurements of the average time to transfer data to each storage device. The updated transfer time measurements are based upon a moving average with adjustable weighting of past and present measurements enabling the system to adapt to changing conditions.

Abstract: Disclosed are a system, a method, and a computer program product to efficiently create consistent transaction sets to maintain one or more copies of data at different data storage sites. All transactions sent to a primary backup appliance during a consistent transaction set creation interval are formed into a consistent transaction set by efficiently adding new transactions as they are received and removing unnecessary transfers as newer versions arrive. When the creation interval has expired, the complete consistent transaction set is transferred to a secondary backup appliance to be used to update a consistent backup copy of the primary site data. For each consistent transaction set, there will be a tree data structure (a search tree) created that contains the addressing information for all of the blocks of data in the consistent transaction set.