Abstract: Various embodiments of systems and methods are disclosed for performing online backup and restore of volume configuration information. In some embodiments, a method involves receiving a request to restore a volume configuration and, in response to the request, writing volume configuration information to a storage device. The volume configuration information includes a first disk signature, which identifies the storage device.

Abstract: A system and method for data storage in an array. A system includes a client coupled to a storage subsystem. The storage subsystem comprises data storage locations addressable as rows and columns in an array. Each column comprises a separate storage device. Each row includes redundant data. For a given row, a coordinating storage device receives data from the client, coordinates computation and storage of redundant data, and forwards data to other storage devices. In response to receiving data targeted for storage in a given storage location, a non-volatile, temporary storage device that is associated with the separate storage device that includes the given storage location buffers the received data. The coordinating storage device conveys a write completion message to the client in response to detecting that the data has been buffered in the non-volatile, temporary storage devices. At least two storage devices are coordinating storage devices in separate rows.

Abstract: A computer accessible medium comprises instructions which, when executed, receive a request to allocate one or more blocks for a file. At least one allocation policy is assigned to the file, wherein the allocation policy specifies one or more storage units on which the blocks are to be allocated. Additionally, if more than one storage unit is specified, the allocation policy includes a control indication indicating a mechanism for selecting among the storage units. The instructions, when executed, may also allocate blocks according to the allocation policy. In another implementation, a computer accessible medium comprises instructions which, when executed receive a request to allocate one or more blocks for a file in a filesystem and allocate blocks according to an allocation policy. Allocation policies are specifiable at two or more levels of granularity in the filesystem.

Abstract: Various systems and methods for performing coordinated distributed write logging are provided. A method may involve one of several hosts, each of which has an associated log, requesting permission to perform a write to data in a storage volume from a coordinator. The coordinator coordinates access to the storage volume between the hosts. Prior to receipt of a response from the coordinator granting permission to perform the write to the storage volume, the host may initiate logging the write data for the write to a respective log. The host may signal completion of the write to an application that initiated the write in response to both logging the write data to the respective log and receiving the response from the coordinator. The host may perform one or more underlying block operations to update the storage volume according to the write subsequent to signaling completion of the write to the application that initiated the write.

Abstract: Systems and methods for I/O fencing in a shared storage environment are provided. Prior to initiating an I/O request, when feasible, the current time from a local timer is compared to the current state of an interval obtained for the target device. As a result, a device reset occurring while the interval is viable does not arbitrarily end a multiphase I/O operation. However, a device reset occurring once the lease has expired results in a delay or termination of the multiphase I/O operation. As a result, multiphase I/O operations from initiating hosts that have lost contact with the shared storage environment are not allowed to corrupt the shared storage devices.

Abstract: One method of updating a change track map involves resetting a mirror recovery map for a data volume. Just before the mirror recovery map is reset, a change track map for the data volume can be updated, using the mirror recovery map. The mirror recovery map can be reset by a data element of a data processing system, while the change track map can be updated by a control element of the data processing system.

Abstract: A system for securing kernel metadata communication in environments employing distributed software services includes a first and a second host linked by a network, where a distributed software service stack at each host includes a respective user-mode software layer and a respective kernel-mode software layer. The first host may be configured to establish a user-mode connection with the second host, e.g., using a secure user-mode communication protocol such as SSL (Secure Sockets Layer). The first and the second hosts may then exchange respective security keys over the secure user-mode connection, upload the security keys to the respective kernel-mode software layers, and use the security keys to secure communication over a kernel-mode connection between the two hosts.

Abstract: Data from a first mirror of a data volume is returned to the computer system in response to receiving the first read request. Additionally, data from second mirror of the data volume is read in response to receiving the first read request. The data read from the second mirror may be stored in a cache memory. The computer system may check the returned data to determine whether it is corrupted. If corrupted, the computer system sends a second read request for the same data. Rather than returning the same corrupted data stored in the first mirror, a copy of the requested data is returned from the cache memory.

Abstract: A system for communication using emulated LUN blocks in storage virtualization environments includes a first host and an off-host virtualizer. The off-host virtualizer may be configured to generate operating system metadata for a virtual storage device, and to make the operating system metadata accessible to the first host. A first layer of a storage software stack at the host may use the operating system metadata to detect the existence of the virtual storage device as an addressable storage device. The off-host virtualizer may also be configured to provide configuration information at a designated set of block addresses within the virtual storage device. A second layer of the storage software stack may be configured to read the configuration information from the designated set of blocks.

Abstract: A system for host-based virtualization optimizations in storage environments employing off-host virtualization may include a host, one or more physical storage devices, and an off-host virtualizer such as a virtualizing switch. The off-host virtualizer may be configured to aggregate storage within the one or more physical storage devices into a virtual storage device such as a logical volume, and to provide control data for the virtual storage device to the host. The host may be configured to use the control data to perform a function in response to an I/O request from a storage consumer directed at the virtual storage device, and to use a result of the function to coordinate one or more I/O operations corresponding to the I/O request.

Abstract: A method, system, computer system, and computer-readable medium to classify a storage device on a SAN prior to allocating the storage device for data storage. A device accessible via a storage area network is detected, and access to the device by a node on the storage area network is established. The device is accessed by a recognizer to determine the type of the device and information about contents of the device. The type of the device can be checked for compatibility with a requester sending a request for a storage device. By checking the compatibility between storage devices and nodes before allocation, spending resources to allocate incompatible storage is avoided and costs of storage management are reduced. Classification information about devices and nodes can be stored in a persistent data store that can be accessed by nodes connected to the SAN.

Abstract: Disclosed is an apparatus and method for transforming unrelated data volumes into related data volumes. The present invention is employed after creation of first and second unrelated data volumes. In one embodiment, the second data volume is refreshed to the data contents of the first data volume so that the second data becomes a PIT copy of the first data volume. Refreshing the second data volume includes overwriting all data of the second data volume with data copied from the first data volume. However, before all data of the second data volume is overwritten with data copied from the first data volume, data of the first data volume can be modified.

Abstract: A system for volume replication in a distributed block virtualization environment includes a first and a second set of one or more physical block devices, a first and a second volume server, one or more volume clients, and a replication manager. The first volume server may be configured to aggregate storage in the first set of one or more physical block devices into one or more logical volumes, and to make the one or more logical volumes accessible to the one or more volume clients. The replication manager may be configured to operate in cooperation with the first and second volume servers and the one or more volume clients to maintain a replica of at least a subset of the one or more logical volumes at the second set of one or more physical block devices.

Abstract: A computer system that implements a method for creating a virtual snapshot of a first storage object. A first storage object such as a data volume is created, wherein creating the first storage object includes creating a first storage object description. This first storage object description relates the first storage object to underlying first storage objects or first physical memory regions. After creating the first storage object, a virtual copy of the first storage object is created as a second storage object. Creating the second storage object includes creating a second storage object description, wherein the second storage object description relates the second storage object to the first storage object. The first storage object is transmitted to a first computer system, and the second storage object description is transmitted to a second computer system.

Abstract: A system for asynchronous reads of old data blocks updated through a write-back cache includes a storage device, a write-back cache, a storage consumer, a storage processing node, and device management software. The device management software may be configured to store a new version of a data block in the write-back cache in response to an update request from the first storage consumer and to then send an update completion notification to the first storage consumer. Some time after the update completion notification has been sent, the device management software may be configured to send a previous version of the updated data block to the storage processing node, where it may be required to perform an operation such as a copy-on write operation or a snapshot update.

Abstract: A method, system, computer system, and computer program product to allocate storage resources among multiple logical volumes. In response to a request to perform a set of operations on multiple logical volumes, a set of allocations of available storage space for performing the set of operations is made. At the time of identifying the storage regions to use for each allocation, the remaining operations and the storage regions that would be available for performing the remaining operations are examined. The rules for implementing each of the logical volumes can be evaluated as part of this examination. If it is apparent that one of the remaining operations will fail based upon a particular set of allocations, space allocated for a previous operation can be de-allocated and alternative allocations can be examined to find a set of allocations that enable the request to be performed successfully.

Abstract: A system employing asymmetric distributed block virtualization includes a volume server, a plurality of volume clients, and one or more physical block devices. The volume server aggregates storage in the physical block devices into a logical volume and makes the logical volume accessible to the volume clients for input/output (I/O) operations. In order to manage different I/O access requirements (such as read-only access versus read-write access) of the volume clients, the volume server maintains a different I/O access policy for each volume client to control the kinds of input/output operations that the volume client is allowed to perform on the logical volume.

Abstract: A method, system, computer system and computer program product to synchronize data and a snapshot of the data taken at a given point in time. Persistent data change maps are used to track changes made to data after a snapshot of the data is taken. Changes to the data are tracked using a persistent accumulator map, and changes to the data with respect to a second set of data are tracked using a persistent volume map. The persistent accumulator map is updated with each update of the data. Persistent volume maps are updated when a subsequent snapshot of the data is taken. Only changes to the data made after the snapshot was taken are applied to synchronize the snapshot with the data so that all of the data is not copied. Snapshots can be located in a physically separate location from the data itself.

Abstract: A volume server for flexibly combining mirroring, striping and concatenation in virtual storage devices includes virtualization functionality and a layout table. The virtualization functionality may be configured to aggregate storage within one or more block devices into a logical volume. The layout table may include multiple extent entries, where each extent entry represents a mapping of an extent of block device storage to a virtual address range of the logical volume, including an indication of a stripe of the logical volume to which the extent is mapped. An overlap in virtual address range between a first and a second extent entry may indicate mirroring of the overlapping blocks at each extent. In response to a storage request, the virtualization functionality may obtain a block device address corresponding to the logical volume virtual address of the storage request from the layout table.

Abstract: A first read request is received from a computer system. Data from one mirror of a data volume is returned to the computer system in response to receiving the first read request. The computer system may check the returned data to determine whether it is corrupted. If corrupted, the computer system sends a second read request for the same data. Rather than returning the same corrupted data stored in the one mirror, a copy of the requested data is returned from an alternate mirror of the data volume.