Abstract: A method for communicating between devices in a network includes creating an I/O tunnel between a first device and a second device through the network. The I/O tunnel is associated with I/O resources in both the first device and the second device, and wherein at least one of the I/O resources comprises a buffer resource. A data transfer operation may be sent between the first device and the second device by consuming at least some of the I/O resources associated with the I/O tunnel. A plurality of commands or a plurality of responses can be aggregated into a single buffer resource. Upon completion of the data transfer operation, the I/O resources that are consumed are automatically renewed.

Abstract: A method for communicating between devices in a network includes creating an I/O tunnel between a first device and a second device through the network. The I/O tunnel is associated with I/O resources in both the first device and the second device, and wherein at least one of the I/O resources comprises a buffer resource. A data transfer operation may be sent between the first device and the second device by consuming at least some of the I/O resources associated with the I/O tunnel. A plurality of commands or a plurality of responses can be aggregated into a single buffer resource. Upon completion of the data transfer operation, the I/O resources that are consumed are automatically renewed.

Abstract: A system for communicating between two devices in a network in which a semi-persistent tunnel is established between the two devices in advance of data communication. The semi-persistent tunnel includes resources that are pre-allocated in a first device at a first end of the communication link by a second device at the second end of the communication link. The first and second devices implement a plurality of processes for handling data transfer operations. Preferably, the semi-persistent tunnel also includes resources that are pre-allocated in a device at the second end of the communication link by the device at the first end of the communication link to allow bi-directional communication. Data transfer operations transmitted through the tunnel include an identification of specific resources of the pre-allocated resources that are to handle the data transfer operation.

Abstract: A data storage system adapted to maintain redundant data storage sets at a destination location(s) is disclosed. The data storage system establishes a copy set comprising a source volume and a destination volume. Data written to a source volume is automatically copied to the destination volume. The data storage system maintains a data log that may be activated when the destination volume is inaccessible due to, for example, a malfunction in the destination storage system or in the communication link between the source system and the destination system. I/O commands and the data associated with those commands are written to the data log, and after a destination system becomes available the information in the data log is merged into the destination volume to conform the data in the destination volume to the data in the source volume. The data log competes for disk capacity with other volumes on the system, and log memory is allocated as needed.

Abstract: A system in which data operations for a data replication group are received in-order, and buffered. When the operations are complete, they are stored in a non-volatile memory atomically with a group sequence number. The cache is preferably mirrored. This creates a persistent association between the data operation and the sequence number. After the atomic store is performed in at least one non-volatile cache, the data operation is propagated to another member of the data replication group along with the group sequence number. In the other member, the data operation is cached at least once in a non-volatile cache atomically with the group sequence number. In this manner, the set of group sequence numbers for a plurality of operations forms a continuous ordering of the data operations.

Abstract: A method of managing storage comprises connecting a number of virtual disks to a disk controller loop of a disk controller, and mounting a portion of the number of virtual disks to the disk controller wherein a storage map is loaded into a fixed-size memory of the disk controller for each virtual disk mounted. The method further comprises receiving a request for data contained on an unmounted virtual disk with the unmounted virtual disk having a storage map of certain size. A sufficient number of mounted virtual disks are dismounted to allow the fixed-size memory to accommodate the certain size of the unmounted virtual disk storage map. The unmounted virtual disk may be mounted.

Abstract: A storage system permits virtual storage of user data by implementing a logical disk mapping structure that provides access to user data stored on physical storage media and methods for generating point-in-time copies, or snapshots, of logical disks. A snapshot logical disk is referred to as a predecessor logical disk and the original logical disk is referred to as a successor logical disk. Creating a snapshot involves creating predecessor logical disk mapping data structures and populating the data structures with metadata that maps the predecessor logical disk to the user data stored on physical media. Logical disks include metadata that indicates whether user information is shared between logical disks. Multiple generations of snapshots may be created, and user data may be shared between these generations. Methods are disclosed for maintaining data accuracy when write I/O operations are directed to a logical disk.

Abstract: A data storage system adapted to maintain redundant data storage sets at a destination location(s) is disclosed. The data storage system establishes a copy set comprising a source volume and a destination volume. Data written to a source volume is automatically copied to the destination volume. The data storage system maintains a data log that may be activated when the destination volume is inaccessible due to, for example, a malfunction in the destination storage system or in the communication link between the source system and the destination system. I/O commands and the data associated with those commands are written to the data log, and after a destination system becomes available the information in the data log is merged into the destination volume to conform the data in the destination volume to the data in the source volume. The data log competes for disk capacity with other volumes on the system, and log memory is allocated as needed.

Abstract: Methods of determining the maximum storage capacity in a storage system that implements RAID-5 redundancy are described. In one implementation the method comprises determining a chunk size of addressable physical storage segments available for allocation in a redundant storage set comprising a plurality of physical disk drives; determining a number of redundant storage units per disk using the chunk size; determining a disk contribution value for each disk in the storage set; and allocating physical storage segments on the plurality of physical drives in accordance with the disk contribution value.

Abstract: Methods of data leveling in a virtualized storage system are described. In one implementation, the method comprises detecting an event that changes the eligible storage capacity of a storage system, and, in response to the event: determining a disk critical ratio for each disk in a group of disks in the storage system; determining an RSS critical ratio for a plurality of RSSs in the storage system; and moving data in the storage system in accordance with at least one of the RSS critical ratio and the disk critical ratio.

Abstract: Methods and systems for managing disk capacity allocated to a data log in a source data storage system during a merge process are disclosed. Data in the data log may be merged into corresponding data on a destination storage system connected to the source data storage system by at least one communication link. In one embodiment a method comprises maintaining a ratio of merge writes out of the data log to writes from a host computer into the data log within a desired range until the write process reaches a predetermined distance from the end of the data log, and quiescing writes from a host computer into the data log until the data log is fully written to the destination storage system.

Abstract: A method of managing storage comprises connecting a number of virtual disks to a disk controller loop of a disk controller, and mounting a portion of the number of virtual disks to the disk controller wherein a storage map is loaded into a fixed-size memory of the disk controller for each virtual disk mounted. The method further comprises receiving a request for data contained on an unmounted virtual disk with the unmounted virtual disk having a storage map of certain size. A sufficient number of mounted virtual disks are dismounted to allow the fixed-size memory to accommodate the certain size of the unmounted virtual disk storage map. The unmounted virtual disk may be mounted.

Abstract: In a storage apparatus, a logic is adapted to write to disk group metadata information including state information that self-identifies state of the disk group and enables a disk controller to load and present virtual disks corresponding to the disk group as logical units to a client in the absence of disk group state information contained in the disk controller.

Abstract: Systems, methods and software for implementing a virtualized storage system. Physical storage is carved into units called physical segments. Logical storage is implemented in atomic logical units called RStores comprising a range of virtual address space that when allocated, is bound to a particular group of PSEGs. RStores preferably implement a selected of data protection. A pool of physical storage devices is carved into redundant storage sets. A plurality of RStores make up a logical disk that is presented to a user. Storage access requests expressed in terms of logical disk addresses are mapped to PSEGs containing data represented by the logical addresses through a split-directory representation of the logical unit.

Abstract: Methods and systems for managing disk capacity allocated to a data log in a source data storage system during a merge process are disclosed. Data in the data log may be merged into corresponding data on a destination storage system connected to the source data storage system by at least one communication link. In one embodiment a method comprises maintaining a ratio of merge writes out of the data log to writes from a host computer into the data log within a desired range until the write process reaches a predetermined distance from the end of the data log, and quiescing writes from a host computer into the data log until the data log is fully written to the destination storage system.

Abstract: A data storage system adapted to maintain redundant data storage sets at a destination location(s) is disclosed. The data storage system establishes a copy set comprising a source volume and a destination volume. Data written to a source volume is automatically copied to the destination volume. The data storage system maintains a data log that may be activated when the destination volume is inaccessible due to, for example, a malfunction in the destination storage system or in the communication link between the source system and the destination system. I/O commands and the data associated with those commands are written to the data log, and after a destination system becomes available the information in the data log is merged into the destination volume to conform the data in the destination volume to the data in the source volume. The data log competes for disk capacity with other volumes on the system, and log memory is allocated as needed.

Abstract: A system and method for replicating data between a plurality of storage locations. Each storage location has a controller with a port to a data communication network and a pool of storage. A logical unit (LUN) of storage is implemented at each storage location such that each implemented LUN comprises a substantially complete replica of the data stored in each other LUN. At least two of the controllers at the plurality of storage locations present their implemented LUN as an active device to the one or more host systems for receiving operational data access requests. Preferably, there are three or more storage locations in the system. Preferably, there are three or more storage locations in the system and each storage location can behave as a source location or a destination location for a particular operational data transaction.

Abstract: A data storage system adapted to maintain redundant data storage sets at a destination location(s) is disclosed. The data storage system establishes a copy set comprising a source volume and a destination volume. Data written to a source volume is automatically copied to the destination volume. The data storage system maintains a data log that may be activated when the destination volume is inaccessible due to, for example, a malfunction in the destination storage system or in the communication link between the source system and the destination system. I/O commands and the data associated with those commands are written to the data log, and after a destination system becomes available the information in the data log is merged into the destination volume to conform the data in the destination volume to the data in the source volume. The data log competes for disk capacity with other volumes on the system, and log memory is allocated as needed.

Abstract: A data replication management (DRM) architecture comprising a plurality of storage cells interconnected by a fabric. Flexibility in connectivity is provided by configuring each storage cell port to the fabric to handle both host data access requests and DRM traffic. Each storage cell comprises one or more storage controllers that can be connected to the fabric in any combination. Processes executing in the storage controller find a path to a desired destination storage cell. The discovery algorithm implements a link service that exchanges information related to DRM between the storage controllers. The DRM architecture is symmetric and peer cooperative such that each controller and storage cell can function as a source and a destination of replicated data. The DRM architecture supports parallel and serial “fan-out” to multiple destinations, whereby the multiple storage cells may implement data replicas.

Abstract: A data replication management (DRM) architecture comprising a plurality of storage cells interconnected by a fabric. Flexibility in connectivity is provided by configuring each storage cell port to the fabric to handle both host data access requests and DRM traffic. Each storage cell comprises one or more storage controllers that can be connected to the fabric in any combination. Processes executing in the storage controller find a path to a desired destination storage cell. The discovery algorithm implements a link service that exchanges information related to DRM between the storage controllers. The DRM architecture is symmetric and peer cooperative such that each controller and storage cell can function as a source and a destination of replicated data. The DRM architecture supports parallel and serial “fan-out” to multiple destinations, whereby the multiple storage cells may implement data replicas.