Abstract: Technologies are described herein for accelerating the boot process of client computers by consolidating client-specific boot data in a data storage system. Boot statistics are collected for a number of client computers booting from virtual storage volumes provided by the data storage system. The boot statistics are analyzed to identify client-specific boot data stored on each of the virtual storage volumes, and the client-specific boot data is consolidated and copied into contiguous regions of a single, consolidated boot volume in the data storage system. Requests for read operations from the client computers for the client-specific boot data are then redirected to the consolidated boot volume, increasing boot performance for the client computers.

Abstract: Systems, methods, and computer-readable media for intelligent distribution of data in a storage cluster are described herein. An example method includes maintaining a cluster volume table (CVT) that stores information regarding data distribution of a volume across a plurality of storage nodes, and defining data distribution groups within the CVT. The CVT includes a plurality of entries, where each entry identifies an owner storage node for a respective logical block of the volume. Each data distribution group includes consecutive CVT entries. The method also includes receiving an input/output (I/O) operation directed to a region of the volume, identifying an owner storage node associated with the region of the volume using the CVT, and serving the I/O operation with at least one storage node of a data distribution group associated with the owner storage node. The I/O operation is served at a chunk-level granularity that is finer than a logical-block-level granularity of the volume.

Abstract: An example computer-implemented method for performing failover operations in a data storage system is described herein. The data storage system can include a first storage controller and a second storage controller for processing input/output (“I/O”) operations for the data storage system. The method can include, in response to a failure of the first storage controller, performing failover operations with the second storage controller, and processing the I/O operations with the second storage controller. The failover operations can include preparing a disk subsystem layer for I/O operations, preparing a device manager layer for the I/O operations, and preparing a network layer for the I/O operations. The disk subsystem, device manager, and network layers can be prepared for the I/O operations without dependencies. In particular, preparation of the network layer is not dependent on preparation of the disk subsystem layer or the device manager layer.

Abstract: A method for performing cache flushing operations in a data storage system can include maintaining a plurality of SSDs as a cache medium for a data storage medium, controlling a region of the SSDs in a write-back cache mode, and monitoring a status of the SSDs to detect a low-performance condition. In the write-back cache mode, data is mirrored across the SSDs. The method can also include performing normal purge operations on the data stored in the region under a condition that the low-performance condition is not detected, and performing aggressive purge operations on the data stored in the region in response to detecting the low-performance condition. The normal purge operations can include flushing the data stored in the region to the data storage medium. The aggressive purge operations can include sequentially mirroring the data stored in the region to one or more special territories of the data storage medium.

Abstract: Technologies are described for implementing a default migration mechanism in a storage system containing multiple tiers of storage with each tier having different cost and performance parameters. Data that is accessed more frequently can be migrated toward higher performance storage tiers while data that is accessed less frequently can be migrated towards lower performance storage tiers. Default migration behavior can be overridden by user-specified values for tier age residency policy, demotion policy, tier occupancy of volumes, and tier assignment. Data migration can be paused by the user and resumed by the user.

Abstract: Technologies are described for implementing a default migration mechanism in a storage system containing multiple tiers of storage with each tier having different cost and performance parameters. Data that is accessed more frequently can be migrated toward higher performance storage tiers while data that is accessed less frequently can be migrated towards lower performance storage tiers. Default migration behavior can be overridden by user-specified values for tier age residency policy, demotion policy, tier occupancy of volumes, and tier assignment. Data migration can be paused by the user and resumed by the user.

Abstract: Technologies are described for implementing a default migration mechanism in a storage system containing multiple tiers of storage with each tier having different cost and performance parameters. Data that is accessed more frequently can be migrated toward higher performance storage tiers while data that is accessed less frequently can be migrated towards lower performance storage tiers. Default migration behavior can be overridden by user-specified values for tier age residency policy, demotion policy, tier occupancy of volumes, and tier assignment. Data migration can be paused by the user and resumed by the user.

Abstract: Technologies are provided for reclaiming a file system coupled to a block device. In these technologies, a dummy file is created. The dummy file is expanded to fill a volume in the block device. A mapping of the dummy file to locations in the volume is retrieved. When the mapping of the dummy file to the locations in the volume is retrieved, corresponding space in the volume is reclaimed. This space may include the locations in the volume corresponding to the mapping of the dummy file. When this space in the volume is reclaimed, the dummy file is deleted.

Abstract: Technologies are described herein for accelerating the boot process of client computers by consolidating client-specific boot data in a data storage system. Boot statistics are collected for a number of client computers booting from virtual storage volumes provided by the data storage system. The boot statistics are analyzed to identify client-specific boot data stored on each of the virtual storage volumes, and the client-specific boot data is consolidated and copied into contiguous regions of a single, consolidated boot volume in the data storage system. Requests for read operations from the client computers for the client-specific boot data are then redirected to the consolidated boot volume, increasing boot performance for the client computers.

Abstract: Technologies are described herein for accelerating the boot process of client computers by consolidating client-specific boot data in a data storage system. Boot statistics are collected for a number of client computers booting from virtual storage volumes provided by the data storage system. The boot statistics are analyzed to identify client-specific boot data stored on each of the virtual storage volumes, and the client-specific boot data is consolidated and copied into contiguous regions of a single, consolidated boot volume in the data storage system. Requests for read operations from the client computers for the client-specific boot data are then redirected to the consolidated boot volume, increasing boot performance for the client computers.

Abstract: Technologies are described herein for boot caching to accelerate boot access in a data storage system providing boot consolidation. Boot caching may be provided to improve boot access for multiple clients concurrently booting from a common storage server. Boot statistics may be collected per user or client. The boot statistics can determine common patterns within the boot procedures of the clients and may be used to compute boot caching tables. These tables may then be used during boot caching to accelerate booting of clients. A boot caching mechanism can be implemented to support improved booting performance by caching data blocks common to multiple booting volumes. This approach can leverage the condition that much of the data loaded by clients at boot time may be substantially identical, because booting can involve loading the same operating system components into each client.

Abstract: A system, method, apparatus, and computer-readable medium are described for providing redundancy in a storage system. According to one method, maps are generated and stored that define stripe patterns for storing data on the storage nodes of a storage cluster. The maps are defined such that when a new storage node is added to the cluster, no movement of data occurs between two storage nodes that existed in the cluster prior to the addition of the new storage node during re-striping, and such that the data stored on each storage node is mirrored on another storage node. Storage nodes may also be designated as an owner or a peer for each storage zone. Input/output operations received at an owner node are fielded directly and mirrored to the peer node, while input/output operations received at a peer node are redirected to the owner node for processing.

Abstract: Technologies are provided for reclaiming a file system coupled to a block device. In these technologies, a dummy file is created. The dummy file is expanded to fill a volume in the block device. A mapping of the dummy file to locations in the volume is retrieved. When the mapping of the dummy file to the locations in the volume is retrieved, corresponding space in the volume is reclaimed. This space may include the locations in the volume corresponding to the mapping of the dummy file. When this space in the volume is reclaimed, the dummy file is deleted.

Abstract: Technologies are described herein for boot caching to accelerate boot access in a data storage system providing boot consolidation. Boot caching may be provided to improve boot access for multiple clients concurrently booting from a common storage server. Boot statistics may be collected per user or client. The boot statistics can determine common patterns within the boot procedures of the clients and may be used to compute boot caching tables. These tables may then be used during boot caching to accelerate booting of clients. A boot caching mechanism can be implemented to support improved booting performance by caching data blocks common to multiple booting volumes. This approach can leverage the condition that much of the data loaded by clients at boot time may be substantially identical, because booting can involve loading the same operating system components into each client.

Abstract: A method, system, apparatus, and computer-readable medium are provided for taking snapshots of a storage volume. According to aspects of one method, each snapshot is represented as a unique sequence number. Every fresh write access to a volume in a new snapshot lifetime is allocated a new section in the disk, called a provision, which is labeled with the sequence number. Read-modify-write operations are performed on a sub-provision level at the granularity of a chunk. Because each provision contains chunks with valid data and chunks with invalid data, a bitmap is utilized to identify the valid and invalid chunks with each provision. Provisions corresponding to different snapshots are arranged in a linked list. Branches from the linked list can be created for storing writable snapshots. Provisions may also be deleted and rolled back by manipulating the contents of the linked lists.

Abstract: A method, system, apparatus, and computer-readable medium are provided for taking snapshots of a storage volume. According to aspects of one method, each snapshot is represented as a unique sequence number. Every fresh write access to a volume in a new snapshot lifetime is allocated a new section in the disk, called a provision, which is labeled with the sequence number. Read-modify-write operations are performed on a sub-provision level at the granularity of a chunk. Because each provision contains chunks with valid data and chunks with invalid data, a bitmap is utilized to identify the valid and invalid chunks with each provision. Provisions corresponding to different snapshots are arranged in a linked list. Branches from the linked list can be created for storing writable snapshots. Provisions may also be deleted and rolled back by manipulating the contents of the linked lists.

Abstract: A system, method, apparatus, and computer-readable medium are described for providing redundancy in a storage system. According to one method, maps are generated and stored that define stripe patterns for storing data on the storage nodes of a storage cluster. The maps are defined such that when a new storage node is added to the cluster, no movement of data occurs between two storage nodes that existed in the cluster prior to the addition of the new storage node during re-striping, and such that the data stored on each storage node is mirrored on another storage node. Storage nodes may also be designated as an owner or a peer for each storage zone. Input/output operations received at an owner node are fielded directly and mirrored to the peer node, while input/output operations received at a peer node are redirected to the owner node for processing.

Abstract: A method, system, apparatus, and computer-readable medium are provided for improved maintenance of metadata relating to a mass storage array. The metadata may comprise the data structures utilized by a thin provisioning system. When the metadata changes, such as in response to the modification of the underlying data, changed metadata is created in the memory. A parity block is then read from the row of the array where the changed metadata is to be stored. A new parity is calculated for the row using only the old metadata, the changed metadata, and the parity read from the stripe. The old metadata need not be read from disk expressly, as is usually done. Instead, the value that is present in memory before the metadata change is utilized directly to calculate the new parity. The changed metadata and the new parity are then written to the array.

Abstract: A method, system, apparatus, and computer-readable medium are provided for taking snapshots of a storage volume. According to aspects of one method, each snapshot is represented as a unique sequence number. Every fresh write access to a volume in a new snapshot lifetime is allocated a new section in the disk, called a provision, which is labeled with the sequence number. Read-modify-write operations are performed on a sub-provision level at the granularity of a chunk. Because each provision contains chunks with valid data and chunks with invalid data, a bitmap is utilized to identify the valid and invalid chunks with each provision. Provisions corresponding to different snapshots are arranged in a linked list. Branches from the linked list can be created for storing writable snapshots. Provisions may also be deleted and rolled back by manipulating the contents of the linked lists.

Abstract: A system, method, apparatus, and computer-readable medium are provided for expanding the data storage capacity of a virtualized storage system, such as a storage cluster. According to one method, maps are generated and stored that define a stripe pattern for storing data on the storage nodes of a storage cluster. The stripe pattern for each map is defined such that when a storage node is added to a cluster and the data is re-striped according to the new map, only the data that will subsequently reside in the new storage node is moved to the new storage cluster during re-striping. The stripe pattern may be further defined so that during re-striping no movement of data occurs between two storage nodes that existed in the cluster prior to the addition of the new storage node. The stripe pattern may be further defined such that during re-striping an equal amount of data is moved from each of the storage nodes that existed in the cluster prior to the addition of the new storage node to the new storage node.