Abstract: Storage locations in a first tier of a multi-tier storage system are allocated to a first set of data structures (e.g., inodes) in a first file set. A file that is stored in the first tier is associated with a first data structure of the first set. In response to determining that data in the file should be moved to a second tier of the multi-tier storage system, the file is associated with a second data structure in a second file set. The second data structure is allocated a storage location in the second tier. Consequently, two data structures are associated with the file. The data is copied from the first tier to the storage location in the second tier, and can be subsequently accessed using the second data structure.

Abstract: An embodiment of the invention provides an apparatus comprising: a hypervisor comprising a virtual caching appliance (VCA) and an intermediate multipathing module that interfaces with VCA; wherein the intermediate multipathing module is configured to pass an I/O request from a virtual machine to the VCA; and wherein the VCA is configured to determine if the I/O request is to be passed from the VCA to a solid state storage or if the I/O request is to be passed from the VCA to a hard disk storage. Another embodiment of the invention provides a method comprising: passing an I/O request from a virtual machine to a virtual caching appliance (VCA) in a hypervisor; and determining if the I/O request is to be passed from the VCA to a solid state storage or if the I/O request is to be passed from the VCA to a hard disk storage.

Abstract: A file system that includes multiple logical devices can be subdivided into multiple containers. The containers each include respective non-overlapping sets of the logical devices. An amount of memory allocated to a container is dynamic. A set of the containers can be selected for a file system consistency check. The file system consistency check is performed on only the set of the containers instead of on the entire file system.

Abstract: A region of memory is logically divided into a number of segments, each of which is logically divided into a number of blocks. Blocks are allocated sequentially. A head pointer and a tail pointer demarcate the section of allocated blocks. As allocated blocks are added, the tail pointer is moved so that it remains at the end of the section of allocated blocks. If the tail pointer is within a threshold distance of the head pointer, then the head pointer is moved from its current position to a new position, and the allocated blocks between the current and new positions are freed (deallocated and/or erased). Thus, writes to the memory can be performed sequentially, and blocks can be freed in advance of when they are actually needed.

Abstract: Various systems and methods for placing a virtual machine on one of a plurality of candidate physical machines. For example, one method can involve generating a list that comprises entries for a virtual machine. Each entry in the list indicates a portion of data that is associated with the virtual machine. The method then involves calculating a number of common entries between the list and each of a plurality of candidate lists, where a common entry is an entry that is included in the respective candidate list and in the list. Each candidate list is associated with a computing device. In response to detecting which candidate list has the most common entries, the method involves assigning the virtual machine to the computing device associated with that candidate list.

Abstract: Various systems and methods selectively generate a point-in-time copy of less than all of the data items within a collectively-managed set of data items. One method involves detecting a modification to a first unit of data within a collectively managed set, subsequent to generation of a selective snapshot of the collectively managed set, and then accesses a first tag associated with the first unit of data. Based on a value of the first tag, the method determines whether the first unit of data is included in a subset of the collectively managed set. The subset includes at least two of the units of data and fewer than all of the units of data in the collectively managed set. Based upon whether the unit of data is included in the subset, the method selects whether to preserve an original value of the first unit of data.

Abstract: Systems and methods for copy on write storage conservation are presented. In one embodiment a copy on write storage conservation method includes creating and mounting a snapshot; mounting a snapshot; monitoring interest in the snapshot; initiating a copy on write discard process before a backup or replication is complete; and deleting the snapshot when the backup or replication is complete. In one embodiment the method also includes marking a file as do not copy on write. In one embodiment, the copy on write discard process includes discarding copy on write data when a corresponding read on the file in the snapshot is successful. Initiating a copy on write discard process can be done at a variety of levels (e.g., a file level, an extent level, a block-level, etc.).

Abstract: Methods and systems are disclosed for backup using a metadata virtual hard drive (VHD) and a differential VHD. A particular system includes a memory device that stores files and a backup agent configured to detect changes to the files. The system includes a translation module configured to translate the detected changes into VHD formatted changes and a VHD module configured to write the VHD formatted changes to a metadata VHD stored at the memory device. The VHD module is also configured to generate a differential VHD based on the metadata VHD. A network interface at the system is configured to transmit the metadata VHD and the differential VHD to a remote storage device.

Abstract: A region of memory is logically divided into a number of segments, each of which is logically divided into a number of blocks. Blocks are allocated sequentially. A head pointer and a tail pointer demarcate the section of allocated blocks. As allocated blocks are added, the tail pointer is moved so that it remains at the end of the section of allocated blocks. If the tail pointer is within a threshold distance of the head pointer, then the head pointer is moved from its current position to a new position, and the allocated blocks between the current and new positions are freed (deallocated and/or erased). Thus, writes to the memory can be performed sequentially, and blocks can be freed in advance of when they are actually needed.

Abstract: Storage locations in a first tier of a multi-tier storage system are allocated to a first set of data structures (e.g., inodes) in a first file set. A file that is stored in the first tier is associated with a first data structure of the first set. In response to determining that data in the file should be moved to a second tier of the multi-tier storage system, the file is associated with a second data structure in a second file set. The second data structure is allocated a storage location in the second tier. Consequently, two data structures are associated with the file. The data is copied from the first tier to the storage location in the second tier, and can be subsequently accessed using the second data structure.

Abstract: Described is a technology by which data is efficiently and securely stored in a single instance store. A hash value is computed from data in its unencrypted form. The hash value is used to reference a single instance of that data when stored in its encrypted form. In this manner, duplicate data blocks are detectable independent of their encryption, yet stored in an encrypted form in a single instance store. In one aspect, context information for decrypting the encrypted data is stored in association with the data. When the client wants to restore the data, the client sends the hash value for that block to the single instance store service. The service returns the block and the associated context information. The client uses the context information to decrypt the block. For example, the context may comprise a key identifier which the client uses to lookup the correct key.

Abstract: Various embodiments of a system and method for performing a file system operation on a specified storage tier are disclosed. Input specifying a file system operation and a pathname may be received. The pathname may include a plurality of components, including one or more directory components and a storage tier component. The pathname may be analyzed to determine a directory specified by the one or more directory components and a storage tier specified by the storage tier component. The file system operation may be performed, where the file system operation operates on the first directory and the first storage tier. In a further embodiment, the components of the pathname may also include a filename component. Thus, the pathname may be further analyzed to determine a filename specified by the filename component. The file system operation may operate on the first filename, the first directory, and the first storage tier.

Abstract: A file system that includes multiple logical devices can be subdivided into multiple containers. The containers each include respective non-overlapping sets of the logical devices. An amount of memory allocated to a container is dynamic. A set of the containers can be selected for a file system consistency check. The file system consistency check is performed on only the set of the containers instead of on the entire file system.

Abstract: Systems and methods for copy on write storage conservation are presented. In one embodiment a copy on write storage conservation method includes creating and mounting a snapshot; mounting a snapshot; monitoring interest in the snapshot; initiating a copy on write discard process before a backup or replication is complete; and deleting the snapshot when the backup or replication is complete. In one embodiment the method also includes marking a file as do not copy on write. In one embodiment, the copy on write discard process includes discarding copy on write data when a corresponding read on the file in the snapshot is successful. Initiating a copy on write discard process can be done at a variety of levels (e.g., a file level, an extent level, a block-level, etc.).

Abstract: Techniques for creating checkpoints are disclosed. In one particular exemplary embodiment, the techniques may be realized as a method for creating file system checkpoints comprising the steps of modifying a first data block and a second data block with a first transaction, associating the first data block with a first stamp, and associating the second data block with a second stamp, wherein the first stamp and the second stamp are substantially similar.

Abstract: Methods and systems are disclosed for backup using a metadata virtual hard drive (VHD) and a differential VHD. A particular system includes a memory device that stores files and a backup agent configured to detect changes to the files. The system includes a translation module configured to translate the detected changes into VHD formatted changes and a VHD module configured to write the VHD formatted changes to a metadata VHD stored at the memory device. The VHD module is also configured to generate a differential VHD based on the metadata VHD. A network interface at the system is configured to transmit the metadata VHD and the differential VHD to a remote storage device.

Abstract: A plurality of data objects may be replicated across a plurality of computing nodes coupled to a network. The network may include a first node operable to initiate an update operation to update a plurality of replicas of a first object. If one or more of the replicas are not reachable then the update operation may update a subset (e.g., a quorum) but not all of the replicas. For each node on which one of the replicas was updated in the update operation, the node may add the object to a list of incoherent objects. The list of incoherent objects may subsequently be used to bring the lagging replicas in sync with the replicas that were updated. In another embodiment, a plurality of replicas of an object may be stored on a plurality of nodes, similarly as described above. A first node that stores a replica of the object may store a first timestamp associated with the replica on the first node.

Abstract: A distributed data object sharing system in which a plurality of data objects are replicated across computing nodes. The system may be operable to identify replica conflicts for the data objects and modify tree structures to reflect the conflicts. In one embodiment, a tree structure may represent a plurality of replica versions. Replica versions in conflict with each other may be represented as child versions at branch points in the tree.

Abstract: A system and method for adaptively responding to update messages for a replica of a data object. A node may maintain first information regarding a replica of a data object. In various embodiments, the first information may comprise any kind of information regarding the replica of the data object. In one embodiment, the first information may comprise information indicative of accesses to the replica of the data object, e.g., may comprise access history information. In response to receiving a message for updating the replica of the data object, the node may respond to the message based on the first information. For example, the node may select one or more operations to perform based on the first information and may perform the one or more selected operations.

Abstract: A file system includes a plurality of entries, wherein each entry is configured to store an indication of data block locations corresponding to a specified file, and wherein each entry is further configured to store an indication of mirrored data block locations corresponding to the specified file. Each entry may include one or more dirty indicators to identify out-of-sync data blocks. In yet another embodiment, the system may be configured to resynchronize a plurality of instances of data blocks depending upon dirty indicators corresponding to the plurality of instances of data blocks.