Abstract: Disclosed is a method, system, program, and data structure for selecting one of multiple data paths to a device. A selection is made of one of multiple paths indicated as enabled to transmit data. A path is indicated as enabled or disabled. Transfer time data is gathered for each enabled path capable of being selected. Paths having transfer time data satisfying a threshold are indicated as disabled. Paths indicated as disabled are not capable of being selected to use to transmit data.

Abstract: The present invention relates to a cache memory management system suitable for use with snapshot applications. The system includes a cache directory including a hash table, hash table elements, cache line descriptors, and cache line functional pointers, and a cache manager running a hashing function that converts a request for data from an application to an index to a first hash table pointer in the hash table. The first hash table pointer in turn points to a first hash table element in a linked list of hash table elements where one of the hash table elements of the linked list of hash table elements points to a first cache line descriptor in the cache directory and a cache memory including a plurality of cache lines, wherein the first cache line descriptor has a one-to-one association with a first cache line.

Abstract: The invention relates to management of I/O in data storage systems. In an embodiment, the invention provides a data storage subsystem processing I/O requests each having a priority, comprising a processor, a memory coupled to the processor, a disk array, an array controller coupled to the processor and the disk array, a network interface, coupled to the processor, to receive an I/O request with a priority, and a program in the memory for managing the I/O request based on the priority, a clip level of the priority, the total workload in the data storage subsystem, and processing I/O requests based on priority, workload clip levels, and fairness levels. The invention also contemplates the use of static and dynamic adjusted clip levels.

Abstract: A system and method for authenticating a host on a network enables the host to update IP configuration and internal configuration of a storage controller connected to the network. The host has an algorithm to decrypt a security key supplied by the storage controller. The host broadcasts a discovery command which includes an IP address of the host and a service requested by the host. The discovery command conforms to a proprietary discovery command protocol. In response to the discovery command, the host receives a response from a storage controller which is able to provide the requested service. The response includes a WWN, IP configuration and a security key of the storage controller, and conforms to the discovery command protocol. Next, the host decrypts the security key received from the storage controller using the decryption algorithm, and sends an updated IP configuration to the storage controller along with the security key for authentication.

Abstract: A method, apparatus and program storage device for allowing continuous availability of data during volume set failures in a mirrored environment. Continuous servicing of input/output request for a volume set having failed on a primary array using either portions of the failed volume set or a mirrored volume set is provided. A determination is made whether the failed volume set can service the input/output request and continuous data availability is provided by using the failed volume set to process the input/output request when the failed volume set can service the input/output request, else using a remote mirrored volume set to process the input/output request.

Abstract: An apparatus, method, and system for speculative data mirroring include a rollback log that receives write data corresponding to a write operation that is directed to a storage region within a source volume. Also included is a storage control module that initiates a lock operation on a corresponding storage region within a target volume and a mirror control module configured to send the data corresponding to the write operation to the target volume without waiting for feedback regarding the lock operation. In one embodiment, initiating a lock operation may include sending a lock command to the target volume. Alternatively, the data corresponding to the write operation may initiate the lock operation. In addition, the mirror control module may initiate retransmission of the data in response to subsequent execution of the lock operation. Due to the unique configuration of the present invention, the present invention reduces latencies arising from synchronous mirroring operations, such as lock operations.

Abstract: Disclosed is a method, system, program, and data structure for updating code in a first and second controllers. The first and second controllers are capable of accessing storage regions in a storage device. The first controller receives a code update and signals the second controller. Access to the first controller is disabled and the code update is applied to the first controller. In response to the signaling, the second controller receives commands directed to all of the storage regions during the code update to the first controller.

Abstract: The invention relates to management of I/O in data storage systems. In an embodiment, the invention provides a data storage subsystem processing I/O requests each having a priority, comprising a processor, a memory coupled to the processor, a disk array, an array controller coupled to the processor and the disk array, a network interface, coupled to the processor, to receive an I/O request with a priority, and a program in the memory for managing the I/O request based on the priority, a clip level of the priority, the total workload in the data storage subsystem, and processing I/O requests based on priority, workload clip levels, and fairness levels. The invention also contemplates the use of static and dynamic adjusted clip levels.

Abstract: An apparatus, system, and process are disclosed for maintaining data in an electronic storage array during multiple, concurrent drive failures. A first drive failure is recognized and the storage system controller subsequently enters a first operating mode. The storage system controller then recognizes a second drive failure and enters a second operating mode, which is different from the first operating mode, in response to the second drive failure. The second operating mode allows the storage system controller and a recovery module to access the data of the second failed drive in a controlled manner in order to attempt to recover the data on the first failed drive. Also, a pinned data module may allow write data to be written to a pinned data drive, instead of a failed drive, while the storage system controller is operating in the second operating mode.

Abstract: Provided is a method, system, and program implemented by a server for controlling and providing access to a file to at least one remote computer over a network. The server maintains metadata about files. The files are maintained at remote storage locations. The server receives a request from the remote computer for a filename of a requested file over the network. The server determines from the metadata one remote storage location address associated with the filename where the requested file is located. The server then updates the metadata for the requested file and sends the storage location address to the remote computer.

Abstract: The present invention relates to system and method of asynchronous data replication. In an embodiment, the system includes a primary host that asynchronously transmits write and sync commands where each write and sync command includes a data set ID and a sequence number. A secondary host coupled to the primary host receives the write and sync commands out of order, tracks receipt of write and sync commands, and after receipt of the write and sync commands of the data set writes blocks associated with the write commands to data storage coupled to the secondary host.

Abstract: The invention relates to snapshots of a data storage system including a host that communicates with a cache memory, source storage, target storage, and metadata, including a source storage for active data, a target storage to store migrated snapshot data, first metadata (e.g., bitmaps and log files with pointers) to indicate when and where the first snapshot data is in target storage, and second metadata (e.g., bitmaps and log files pointers) to indicate when and where the second snapshot data is in target storage where the first and second metadata locate the same snapshot data in the target storage. The invention maintains data consistency when reading metadata for snapshots into host memory, searching the metadata to identify snapshots that require original data to be destaged, destaging the original data to target storage, and updating the metadata to locate the original data and indicate completion of the target destage operation.

Abstract: The present invention relates to a cache memory management system suitable for use with snapshot applications. The system includes a cache directory including a hash table, hash table elements, cache line descriptors, and cache line functional pointers, and a cache manager running a hashing function that converts a request for data from an application to an index to a first hash table pointer in the hash table. The first hash table pointer in turn points to a first hash table element in a linked list of hash table elements where one of the hash table elements of the linked list of hash table elements points to a first cache line descriptor in the cache directory and a cache memory including a plurality of cache lines, wherein the first cache line descriptor has a one-to-one association with a first cache line.

Abstract: A method, apparatus and program storage device for maintaining data consistency and cache coherency during communications failures between nodes in a remote mirror pair. A link between a mirror pair of storage systems is monitored. During a link failure between a first storage system and a second storage systems, reads and writes on the first and second storage systems are independently performed and write data and associated timestamps are maintained for the write data for each write in a queue on the first and second storage system. After link reestablishment, volume sets on the first and second storage systems are resynchronized using write data and associated timestamps.

Abstract: A fault tolerant synchronized virtual memory manager for use in a load sharing environment manages memory allocation, memory mapping, and memory sharing in a first processor, while maintaining synchronization of the memory space of the first processor with the memory space of at least one partner processor. In one embodiment, synchronization is maintained via paging synchronization messages such as a space request message, an allocate memory message, a release memory message, a lock request message, a read header message, a write page message, a sense request message, an allocate read message, an allocate write message, and/or a release pointer message. Paging synchronization facilitates recovery operations without the cost and overhead of prior art fault tolerant systems.

Abstract: Provided is a method, system, and program for initializing a storage device comprising multiple storage units through a storage controller. A request is received to initialize a storage space that spans the storage units. A determination is made of a layout of sets of sequential data blocks of the storage space on the storage units, wherein sets of sequential data blocks are written across the storage units. For each set of sequential data blocks, a determination is made of a block address in each storage unit where a first data block in the set of sequential data blocks will be written. A write command is generated for each of the storage units, wherein each write command indicates the determined block address for the storage unit and a block number. The write command is transmitted with one block of initialization data to the storage unit.

Abstract: Provided is a computer implemented method, system, and program for implementing for implementing a remote method call. Remote objects and at least one proxy object are generated, where each proxy object corresponds to one remote object. Data from the remote object is included into the proxy object. A call to a method on one proxy object is processed and the method is executed. The method is one of a plurality of methods, wherein at least one of the plurality of methods comprises a local method including code to perform method operations on the proxy object without going to the remote object and at least one other of the plurality of methods comprises a remote method including code to perform method operations on the remote object.

Abstract: The invention relates to host caching in data storage systems. In an embodiment, the invention provides a first host and a second host, each having memory. The host memory includes nonvolatile and volatile portions available for cache. Each host logically owns its volatile memory and the other host's nonvolatile memory. By assigning ownership in this way data can be transmitted between the hosts with little communication overhead. In addition, if the first host fails between write acknowledgment and destaging the write data, the write data is safely stored in the second nonvolatile memory of the second host. Thus, the second host can destage the data from the second nonvolatile memory. In addition, the host cache writes and reads the data rapidly by its nature.

Abstract: Provided is a method, system, and program for determining a configuration of a logical array including a plurality of storage devices. A selection of a number of storage devices is received to include in the logical array. A determination is made of a number of groups in which to include the selected number of storage devices, wherein each group includes at least one storage device maintaining user data and parity data for the user data in the group. Determining an assignment of the selected number of storage devices to the determined number of groups and allocating the storage devices to the determined number of groups according to the determined assignment.

Abstract: Disclosed is a method, system, and data structures for updating data in a storage device. An update to one or more blocks of customer data at addresses in the storage device is received. For each block of data to update, metadata is generated indicating the address of the block in the storage device and an error checking code that is capable of being used to determine whether the customer data in the block has changed. For each block of data to update, the block of data to update and the metadata for the block are written to cache. Further, for each block of data to update, the block of data and the metadata are transferred for the block from the cache to the storage device. The metadata may be used during power loss and recovery.