Abstract: A mechanism to support remote mirroring of storage devices by data storage systems in a one-to-many switched environment. Each data storage system includes a disk director that is adapted to control at least one device group that is supported in a mirrored configuration with a corresponding device group controlled by one of the other data storage systems. For each device group and corresponding device group, there are first ports associated with the device group and second ports associated with the corresponding device group. A switch element is adapted to connect one of the first ports to at least one of the second ports so that data may be exchanged between the ports for each device group and corresponding device group. The disk director selects which first port is to be connected to which second port via the switch element in the establishment of a logical link.

Abstract: Method and apparatus are disclosed for a computer system including host computers and storage elements. The host computers may be configured into a host domain and the storage elements configured into a storage domain. The storage domain includes a plurality of primary storage devices and a secondary storage device. The secondary storage device may be coupled to a plurality of the primary storage devices through a network. In another embodiment, the secondary storage device may send and receive information from a heterogeneous set of host computers. In another embodiment, connections for transfer of data onto the secondary storage element are created automatically.

Abstract: Reversing a communication path between a first volume on a first storage device and a second volume on a second storage device includes suspending communication between the first and second volumes while maintaining operations for other volumes of the storage devices, causing the first volume to change from a source volume to a destination volume without destroying the first volume, causing the second volume to change from a destination volume to a source volume without destroying the second volume, and resuming communication between the first and second volumes. Causing the first volume to change from a source volume to a destination volume may include modifying a table of the first storage device. Causing the second volume to change from a source volume to a destination volume may include modifying a table of the second storage device.

Abstract: Reversing a communication path between a first volume on a first storage device and a second volume on a second storage device includes suspending communication between the first and second volumes while maintaining operations for other volumes of the storage devices, causing the first volume to change from a source volume to a destination volume without destroying the first volume, causing the second volume to change from a destination volume to a source volume without destroying the second volume, and resuming communication between the first and second volumes. Causing the first volume to change from a source volume to a destination volume may include modifying a table of the first storage device. Causing the second volume to change from a source volume to a destination volume may include modifying a table of the second storage device.

Abstract: A mechanism to support remote mirroring of storage devices by data storage systems in a one-to-many switched environment. Each data storage system includes a disk director that is adapted to control at least one device group that is supported in a mirrored configuration with a corresponding device group controlled by one of the other data storage systems. For each device group and corresponding device group, there are first ports associated with the device group and second ports associated with the corresponding device group. A switch element is adapted to connect one of the first ports to at least one of the second ports so that data may be exchanged between the ports for each device group and corresponding device group. The disk director selects which first port is to be connected to which second port via the switch element in the establishment of a logical link.

Abstract: A computer system may include one or more hosts and a plurality of data storage devices for providing multihop system calls. The data storage devices are interconnected and also connected to the one or more hosts. The connections may be direct or indirect. Each data storage device classifies a data operation as a system call, a remote system call, or a multihop system call. If an operation is classified as a multihop system call by a first data storage device, a portion of the data associated with the multihop system call is removed and a second portion of the data is forwarded to a second data storage device as specified by a connection identifier included in the first portion. A multi-execute command may be issued by a host system causing one or more commands to be executed on one or more processors at points in a communication path in a forward and/or reverse direction when traversing the communication path.

Abstract: A method for scanning a message-list accessible to a plurality of processors includes retrieving, from a cache associated with a scanning processor from the plurality of processors, information identifying a starting message-slot. This information is then used to begin a scan of the message-list at that starting message-slot. The information indicating the starting message-slot is obtained by identifying, in the message-list, a message-slot containing a message intended for a recipient processor from the plurality of processors and obtaining, from the identified message-slot, information indicative of a location of a succeeding message-slot in the message-list. This information is then cached, for retrieval during a subsequent scan of the message-list.

Abstract: Method and apparatus are disclosed for copying and backing up logical objects in a computer storage system. The logical objects are comprised of data blocks. The data blocks may be copied in any order. The data blocks may be copied or written from a storage media, such as a tape, in parallel.

Abstract: A mechanism to support remote mirroring of storage devices by data storage systems in a one-to-many switched environment. Each data storage system includes a disk director that is adapted to control at least one device group that is supported in a mirrored configuration with a corresponding device group controlled by one of the other data storage systems. For each device group and corresponding device group, there are first ports associated with the device group and second ports associated with the corresponding device group. A switch element is adapted to connect one of the first ports to at least one of the second ports so that data may be exchanged between the ports for each device group and corresponding device group. The disk director selects which first port is to be connected to which second port via the switch element in the establishment of a logical link.

Abstract: Method and apparatus are disclosed for copying and backing up logical objects in a computer storage system. The logical objects are comprised of data blocks. The data blocks may be copied in any order. The data blocks may be copied or written from a storage media, such as a tape, in parallel.

Abstract: Dynamically creating a communication path between first and second storage devices, includes creating a connection to a source volume on the first storage device and indicating that the source volume is not ready to transmit data on the communication path, after successfully creating the connection to the source volume, creating a connection to a destination volume on the second storage device and initially indicating that portions of one of: the destination volume and the source volume do not contain valid copies of data, where the destination volume accepts data from the source volume, and after successfully creating the connections to the source and destination volumes, indicating that the source volume is ready to transmit data on the communication path. Dynamically creating a communication path between first and second storage devices, may also include creating at least one of: the source volume and the destination volume.

Abstract: A method for scanning a message-list accessible to a plurality of processors includes retrieving, from a cache associated with a scanning processor from the plurality of processors, information identifying a starting message-slot. This information is then used to begin a scan of the message-list at that starting message-slot. The information indicating the starting message-slot is obtained by identifying, in the message-list, a message-slot containing a message intended for a recipient processor from the plurality of processors and obtaining, from the identified message-slot, information indicative of a location of a succeeding message-slot in the message-list. This information is then cached, for retrieval during a subsequent scan of the message-list.

Abstract: Dynamically creating a communication path between first and second storage devices, includes creating a connection to a source volume on the first storage device and indicating that the source volume is not ready to transmit data on the communication path, after successfully creating the connection to the source volume, creating a connection to a destination volume on the second storage device and initially indicating that portions of one of: the destination volume and the source volume do not contain valid copies of data, where the destination volume accepts data from the source volume, and after successfully creating the connections to the source and destination volumes, indicating that the source volume is ready to transmit data on the communication path. Dynamically creating a communication path between first and second storage devices, may also include creating at least one of: the source volume and the destination volume.

Abstract: A data transfer arrangement transfers data from a source device, such as a local mass storage facility, to a destination device, such as a remote storage facility. The data transfer arrangement comprises a source device and a destination device. The source device transfers to the destination device a data block including data and padding along with a source check value that is a function of the data and selectively the padding, and a check indication indicating whether the check value is the function of the data alone, or the data and the padding. The destination device, after receiving the data block, source check value and check indication, generates a destination check value that is the function of the data alone, or the data and the padding, based on the check indication, and uses the source and destination check values to determine whether the data block was correctly received.

Abstract: Determining device characteristics includes obtaining a first globally accessible value, if the first globally accessible value corresponds to a stored first value, obtaining device characteristics data from a relatively fast memory, if the first globally accessible value does not correspond to the stored first value, obtaining a second globally accessible value, if the second globally accessible value corresponds to a stored second value, obtaining device characteristics data from a relatively fast memory, if the second globally accessible value does not correspond to the stored second value, obtaining device characteristics data from a relatively slow memory and updating the relatively fast memory, the stored first value, and the stored second value. The globally accessible first value may include device I/O information. The globally accessible values may be stored in global memory that is accessible to a plurality of processors.

Abstract: The invention relates generally to mass storage systems, and in particular to mass storage systems in which stored logical volumes are duplicated in mirrored form. The system includes a method for dynamically maximizing separation of said logical volumes by adjusting the mirror service policy for a disk drive system. Statistics are periodically collected describing the reading and writing of data to mirrored logical volumes of the system in successive time periods and, from time to time, based upon the collected statistics, activity levels for the logical volumes are determined. A matching algorithm, weighted or unweighted, maximizes separation of the logical volumes and minimizes average physical drive seek times. In particular, the system takes into account activity levels at the physical devices and results in more efficient accessing of logical volume pairs as well as a better balance or loading of logical volumes.

Abstract: In a system that includes a back-up subsystem comprising back-up media, a mass storage subsystem connected to the back-up subsystem, and a host connected to the mass storage subsystem, the mass storage subsystem, as master and independent of the host, requests the restore operation by providing to the back-up subsystem, as slave, data identifiers identifying multiple data items to be transferred during the restore operation. The back-up subsystem determines its preferred ordering for retrieval of the requested plurality of data items from the back-up media. The back-up subsystem provides the requested data items to the mass storage subsystem in the determined preferred order in a plurality of iterations, each iteration identified by a data item identifier for the data item to be transferred in the current iteration.

Abstract: Determining device characteristics includes obtaining a first globally accessible value, if the first globally accessible value corresponds to a stored first value, obtaining device characteristics data from a relatively fast memory, if the first globally accessible value does not correspond to the stored first value, obtaining a second globally accessible value, if the second globally accessible value corresponds to a stored second value, obtaining device characteristics data from a relatively fast memory, if the second globally accessible value does not correspond to the stored second value, obtaining device characteristics data from a relatively slow memory and updating the relatively fast memory, the stored first value, and the stored second value. The globally accessible first value may include device I/O information. The globally accessible values may be stored in global memory that is accessible to a plurality of processors.

Abstract: Method and apparatus are disclosed for a computer system including host computers and storage elements. The host computers may be configured into a host domain and the storage elements configured into a storage domain. The storage domain includes a plurality of primary storage devices and a secondary storage device. The secondary storage device may be coupled to a plurality of the primary storage devices through a network. In another embodiment, the secondary storage device may send and receive information from a heterogeneous set of host computers. In another embodiment, connections for transfer of data onto the secondary storage element are created automatically.

Abstract: Determining device characteristics includes obtaining a first globally accessible value, if the first globally accessible value corresponds to a stored first value, obtaining device characteristics data from a relatively fast memory, if the first globally accessible value does not correspond to the stored first value, obtaining a second globally accessible value, if the second globally accessible value corresponds to a stored second value, obtaining device characteristics data from a relatively fast memory, if the second globally accessible value does not correspond to the stored second value, obtaining device characteristics data from a relatively slow memory and updating the relatively fast memory, the stored first value, and the stored second value. The globally accessible first value may include device I/O information. The globally accessible values may be stored in global memory that is accessible to a plurality of processors.