Abstract: A method for establishing and maintaining a differential snapshot of a set of files stored on a volume is disclosed. The invention achieves processing time and disk space optimizations by avoiding copy-on-write operations for logically insignificant moves of blocks, such as the block rearrangements characteristic of defragmentation utilities. A file system enhancement enabling the passing of a block copy command from the file system to lower-level drivers, is used to inform the snapshotter that a block move operation is not logically meaningful. When the logically insignificant move is of a block whose data forms part of the data captured in the snapshot virtual volume, and when the move is to a block location that is functioning as logical free space, the snapshotter can simply modify its block bitmap and update translation table entries without needing to perform a copy-on-write.

Abstract: A mount manager and supporting data structures enable automatic identification and re-establishment of logical volumes on non-removable storage devices in a computer system across multiple reboots and reconfigurations. The mount manager generates a redirected name for a new logical volume when a unique volume identifier is presented to the mount manager by the operating system. The mount manager stores the unique volume identifier and the associated redirected name in a persistent mount manager data structure The mount manager establishes a symbolic link between the persistent redirected name, which is used by higher layers of the operating system and user applications to address the logical volume, and a non-persistent device name used by the operating system.

Abstract: Volume configuration data management systems and methods are described. A logical volume provider maintains an epoch number on each of the extents comprising a volume. Upon each change in the configuration of the volume, the epoch number on each of the currently online extents is updated. When a volume is discovered and a request is made to bring the volume online, the logical volume provider can compare the epoch numbers on the extents to determine if the volume data is consistent across each of the extents, or if an extent contains stale data due to a transitory outage.

Abstract: Systems and methods for performing an on-demand determination of a correct set of volumes to be exported are described. A disk platter is defined to be the unit of volume migration. Volumes are added to the platter based on whether or not the volume coexists on a disk containing a volume to be exported.

Abstract: A storage management system in which a plurality of volume providers maps logical storage volumes onto one or more storage devices within a stand-alone computer or within a storage network. A common volume manager executing on a computer within the storage network selectively communicates commands to one or more of the volume providers in order to control the storage devices. The inventive storage management system seamlessly integrates management of the vendor-specific volume providers. The common volume manager provides a common application programming interface (API) by which applications are able to control and monitor hardware and software volume providers without requiring detailed knowledge of the volume providers or the underlying storage devices. The common volume manager aggregates response information from the volume providers and communicates the aggregated information to the software application that issued the storage management request.

Abstract: A partition manager enables the dynamic creation, reconfiguration, and deletion of logical volumes as non-removable storage devices are connected, reconfigured, or disconnected in a computer system by assigning partitions on a connected device to volume managers which create the logical volumes, and by removing the assignment when the device is disconnected or reconfigured. The partition manager receives notification from the operating system of the arrival of new volume managers in a system. When new partitions are created on a non-removable storage device in the system by a device driver, the partition manager intercepts the partitions before they can be registered with the operating system. The partition manager queries each volume manager, in order of their arrival in the system, as to whether the volume manager handles a particular new partition and assigns control of the partition to the appropriate volume manager.

Abstract: A mount manager and supporting data structures enable automatic identification and re-establishment of logical volumes on non-removable storage devices in a computer system across multiple reboots and reconfigurations. The mount manager generates a redirected name for a new logical volume when a unique volume identifier is presented to the mount manager by the operating system. The mount manager stores the unique volume identifier and the associated redirected name in a persistent mount manager data structure The mount manager establishes a symbolic link between the persistent redirected name, which is used by higher layers of the operating system and user applications to address the logical volume, and a non-persistent device name used by the operating system.

Abstract: A system and method for more efficiently maintaining multiple temporal snapshots of a common base volume. When the base volume is modified, such as when existing data is overwritten with new data, that modification may affect two or more of the snapshots. Before the modification, the existing data is copied only to the differential file associated with the latest snapshot. When a region of a selected snapshot is read, the region is read from the selected snapshot's associated differential file. If the existing data is in the differential file, that data is returned to the reading process. If later snapshots have been taken, data associated with other parts of the region may be stored in one or more of the later differential files.

Abstract: A snapshot system capable of capturing snapshots of multiple volumes wherein the snapshots are coordinated. A snapshot manager determines which volumes are to be involved in a snapshot operation, and issues a message to the file system for each volume involved, each message including information sufficient to identify the volumes involved in the snapshot operation. Each file system passes its respective message down to a coordinator mechanism. The coordinator mechanism coordinates the state of each of the volumes, such as by holding writes thereto, to put each volume into a quiescent state, and then enables the snapshot to be captured. When the snapshots are captured, a snapshot set will include snapshots that are coordinated across the multiple volumes. The coordinator mechanism releases any writes being held for the volumes involved.

Abstract: Systems and methods for creating and maintaining a stacked volume using one more volumes or extents of a storage subsystem is disclosed. The systems and methods define a hierarchy of operations and components that process operations. The hierarchy includes plex operations for an entire volume, mapping operations that concatenate volumes and/or extents, plex operations for a volume or extent that is a sub-component of a stacked volume. The hierarchy also includes striping operations that create and maintain storage volume stripes comprising sub-volumes and/or extents. In addition, the hierarchy includes configuration operations that operate directly on a storage volume through a hardware or software volume provider. Together, the hierarchy defined allows a flexible, extensible mechanism to build stacked volumes that provide for increase performance, fault tolerance, and/or aggregate volume size, while elimination volume combinations that can cause performance problems.

Abstract: Volume configuration data management systems and methods are described. A logical volume provider maintains an epoch number on each of the extents comprising a volume. Upon each change in the configuration of the volume, the epoch number on each of the currently online extents is updated. When a volume is discovered and a request is made to bring the volume online, the logical volume provider can compare the epoch numbers on the extents to determine if the volume data is consistent across each of the extents, or if an extent contains stale data due to a transitory outage.

Abstract: The invention provides a method and system for arbitrating for ownership of a logical quorum resource, such as a logical quorum volume, comprising one or more physical quorum resources so as to form a storage network having a plurality of storage devices. Arbitration and volume management responsibilities are cleanly divided between cluster management software and volume management software. The cluster management software handles the arbitration process without knowing the details of how the logical quorum resource is formed. The volume management software handles the formation and management of the logical quorum volume without having details of the arbitration process.

Abstract: Volume configuration data management systems and methods are described. A logical volume provider maintains an epoch number on each of the extents comprising a volume. Upon each change in the configuration of the volume, the epoch number on each of the currently online extents is updated. When a volume is discovered and a request is made to bring the volume online, the logical volume provider can compare the epoch numbers on the extents to determine if the volume data is consistent across each of the extents, or if an extent contains stale data due to a transitory outage.

Abstract: A method and system for providing remote access and control of devices such as disks, tape drives and modems across a network. A client driver intercepts I/O requests that are destined for a device which an application essentially considers a local device, such as for purposes of disk mirroring. The client driver queues and dequeues the I/O request, marshals it with header information and data, and sends it as a message to the server over one of possibly multiple connections to the server. A server driver unmarshalls the message, places it in a preallocated buffer as designated by the client, and generates an I/O request therefrom directed to the server device. The server responds with a completion status. The client side manages the server buffers, and the client classifies and partitions large requests into one or more segments that fit the server buffers. Sequential processing also may be ensured.

Abstract: A partition manager enables the dynamic creation, reconfiguration, and deletion of logical volumes as non-removable storage devices are connected, reconfigured, or disconnected in a computer system by assigning partitions on a connected device to volume managers which create the logical volumes, and by removing the assignment when the device is disconnected or reconfigured. The partition manager receives notification from the operating system of the arrival of new volume managers in a system. When new partitions are created (“enumerated”) on a non-removable storage device in the system by a device driver, the partition manager intercepts the partitions before they can be registered with the operating system. The partition manager queries each volume manager, in order of their arrival in the system, as to whether the volume manager handles a particular new partition and assigns control of the partition to the appropriate volume manager.

Abstract: Persistent names for logical volumes in a computer system are used to enable symbolic links between the persistent names and non-persistent device names that identify the logical volumes to the lower layers of the operating system during a single boot session. A persistent unique mount name for each logical volume is associated with a unique volume identifier for the logical volume in a persistent mount manager data structure. Optionally a persistent drive letter can be assigned to the volume. Higher layers of the operating system and user applications address a volume through the persistent mount name as well as any assigned drive letter.

Abstract: A mount manager and supporting data structures enable automatic identification and re-establishment of logical volumes on non-removable storage devices in a computer system across multiple reboots and reconfigurations. The mount manager generates a redirected name for a new logical volume when a unique volume identifier is presented to the mount manager by the operating system. The mount manager stores the unique volume identifier and the associated redirected name in a persistent mount manager data structure The mount manager establishes a symbolic link between the persistent redirected name, which is used by higher layers of the operating system and user applications to address the logical volume, and a non-persistent device name used by the operating system.

Abstract: A system and method for creating a snapshot with a differential file maintained on the base volume that can grow as needed. When a snapshot is captured, free space is allocated on the base volume to receive the differential file. Writes to the base volume are allowed except to the free space allocated to the differential file. Then the snapshot is captured. After the snapshot process is complete, data that was originally present at the time the snapshot was captured may be copied to the differential file before it is modified. To grow the differential file out of its allocated space, new free space is selected from the free space currently on the base volume in conjunction with the free space at the time the snapshot was captured. The free space bitmap file of the snapshot volume may be used to identify the free space at the time the snapshot was captured.

Abstract: Information regarding volume mount points hosted by a logical volume are stored on the physical device underlying the logical volume so that the relationships between the host logical volume and target logical volumes mounted on the volume mount points can be reconstituted when the system containing the logical volumes is rebooted, when the underlying physical devices are moved with the system, and when the logical volumes are transported to a different system. A data structure stored on the physical device contains the directory name of the volume mount point and the unique identifier and a globally unique mount name of the target logical volume mounted at the volume mount point. When the target logical volume is present in the system, symbolic links are created to relate the volume mount point name to a device name for the target logical volume so that pathnames containing the directory junction name are resolved correctly.

Abstract: Persistent names for logical volumes in a computer system are used to enable symbolic links between the persistent names and non-persistent device names that identify the logical volumes to the lower layers of the operating system during a single boot session. A persistent unique mount name for each logical volume is associated with a unique volume identifier for the logical volume in a persistent mount manager data structure. Optionally a persistent drive letter can be assigned to the volume. Higher layers of the operating system and user applications address a volume through the persistent mount name as well as any assigned drive letter.