Abstract: An apparatus for managing incremental storage includes a storage pool management module that allocates storage volumes to a virtual volume. Also included is an incremental log corresponding to the virtual volume, which maps virtual addresses to storage addresses. The apparatus may also include a replication module that sends replicated data to the virtual volume and a policy management module that determines allocation criteria for the storage pool management module. In one embodiment, the incremental log includes a lookup table that translates read and write requests to physical addresses on storage volumes within the virtual volume. The replicated data may include incremental snapshot data corresponding to one or more primary volumes. The various embodiments of the virtual incremental storage apparatus, method, and system facilitate dynamic adjustment of the storage capacity of the virtual volume to accommodate changing amounts of storage utilization.

Abstract: The present invention relates to systems and methods 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: A message tracker having a transfer monitor, a set of registers, and at least one arithmetic unit increases performance and reliability when transmitting or receiving messages within a computer system. A set of message parameters such as a current address, a remaining length, and a communicated length are stored within the set of registers. The transfer monitor observes data transfers on a multi-tenant bus in order to detect data transfers related to the message and provide an update signal. The message parameters within the registers are updated in response to the update signal. The process of detecting and updating is repeated until the entire message is transferred, and the message tracker then informs a control processor or process that communication of the message has occurred. To facilitate message coalescing, several message trackers may share a message queue that is configured to store message parameters corresponding to completed messages.

Abstract: The invention relates to methods of snapshot operation for a data storage system with a host communicating with a cache memory, a source Virtual Logical Unit Number (VLUN) and a target VLUN, including generating first metadata (e.g., bitmaps and log files pointers) to locate first snapshot data and to indicate when the first snapshot data is in the target VLUN and generating second metadata to locate second snapshot data and to indicate when the second snapshot data is in the target VLUN, wherein the first and second metadata locate the same data in the target VLUN. The invention relates to systems that implement the methods. It relates to destaging data to maintain data consistency including reading metadata for snapshots, searching the metadata to identify snapshots that require original data to be destaged, destaging the original data to target storage, and updating metadata to locate original data and indicate destage completion.

Abstract: Snapshot sets comprising snapshot criteria are created, maintained, and executed via a command set designed to facilitate managing and conducting snapshots on data distributed across multiple volumes. Snapshot criteria such as source volume, target volume, redundancy level, copy mode, and the like are added as desired to a snapshot set. Upon invocation of an execute command, the fast replication operations defined by the snapshot set are executed, providing a logically atomic data replication utility potentially involving multiple sources and targets. In one embodiment auto selection of a target may be specified, thus facilitating over-subscription of target resources. The present invention reduces the complexity of archiving data—particularly data distributed across multiple volumes such as data associated with database applications and the like.

Abstract: An apparatus for managing incremental storage includes a storage pool management module that allocates storage volumes to a virtual volume. Also included is an incremental log corresponding to the virtual volume, which maps virtual addresses to storage addresses. The apparatus may also include a replication module that sends replicated data to the virtual volume and a policy management module that determines allocation criteria for the storage pool management module. In one embodiment, the incremental log includes a lookup table that translates read and write requests to physical addresses on storage volumes within the virtual volume. The replicated data may include incremental snapshot data corresponding to one or more primary volumes. The various embodiments of the virtual incremental storage apparatus, method, and system facilitate dynamic adjustment of the storage capacity of the virtual volume to accommodate changing amounts of storage utilization.

Abstract: A method for managing incremental storage includes a storage pool management module that allocates storage volumes to a virtual volume. Also included is an incremental log corresponding to the virtual volume, which maps virtual addresses to storage addresses. The method may also include a replication module that sends replicated data to the virtual volume and a policy management module that determines allocation criteria for the storage pool management module. In one embodiment, the incremental log includes a look up table that translates read and write requests to physical addresses on storage volumes within the virtual volume. The replicated data may include incremental snapshot data corresponding to one or more primary volumes. The various embodiments of the virtual incremental storage method facilitate dynamic adjustment of the storage capacity of the virtual volume to accommodate changing amounts of storage utilization.

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 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: 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 process, apparatus, and system stores data check information on an electronic storage medium that uses standard sector data field sizes. The check information may include a cyclic redundancy check (CRC), a logical block address (LBA), a longitudinal redundancy check (LRC), state information, a sequence number, or other information to identify data state, misplacement, or corruption. The check information, instead of being appended to the data within the data sector, may be stored in an independent check sector. The check information corresponding to multiple data sectors may also be aggregated and stored in a single check sector. The process or apparatus may be incorporated in a storage system controller, a RAID controller, a software SCSI stack in a computer, an operating system, a storage device driver, or another appropriate application that interfaces with standard and commodity storage system components.

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: 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: A method and apparatus for cache coherency in storage system is disclosed. The invention maintains cache coherency in the controller system of the storage system in a manner to minimize the performance degradation to a host system, and to allow the caches to be coherent without requiring data to be written to the backing disks. Each controller manages an area of memory on the partner controller, but the area is managed dynamically and is done with the information about the partner controller. A first controller determines which mirror cache line on a second controller to copy data into, and then mirrors the data from a first controller cache line to a second controller cache line. A message is sent from the first controller to the second controller informing the second controller of cache meta data associated with the mirror cache line so that the cache line may be added to the second controller's hash table.

Abstract: The present invention is a method and system for upgrading drive firmware on a drive within a distributed data storage system in a manner that is transparent and non-disruptive to the host system operations. The method and system allow for normal read and write operations to occur during the firmware upgrade process, even while the primary disk drive is off-line, through alteration of the controller read and write policies. A mapping file is created on a temporary storage device to reduce the necessary time period of the upgrade process. This time period is further reduced in a mirrored storage system or in a system having a spare drive, where a logging file is created to store the data diverted from the primary disk drive during the upgrade process. An advantage is the ability to maintain storage system redundancy during the upgrade process.