Abstract: A technique provides memory efficient caching of metadata managed by a volume layer of a storage input/output stack executing on one or more nodes of a cluster. Efficient caching of the metadata in a memory of a node may be realized through the use of a caching data structure, i.e., a page cache, configured to store a key-value pair, wherein the key is an extent key and the value is a metadata page containing the index entries. The page cache illustratively includes two data structures configured to maintain the properties of Least Recently Used (LRU) and Least Frequently Used (LFU) for the cache. The first data structure is a hash table that stores a dense tree metadata page (value) indexed by the extent key. The second data structure is a recycle queue that controls the metadata page stored in the hash table based on spatial and temporal locality of the page.

Abstract: A technique enables recovery of storage space trapped in an extent store due to overlapping write requests associated with metadata managed by a volume layer of a storage input/output stack executing on one or more nodes of a cluster. The metadata is organized as a multi-level dense tree metadata structure, wherein each level of the dense tree includes volume metadata entries for storing the metadata. When a level of the dense tree is full, the volume metadata entries of the level are merged with a next lower level of the dense tree in accordance with a dense tree merge operation. The technique may be invoked during the merge operation to process the volume metadata entries associated with the overlapping write requests at each level of the dense tree involved in the merge operation. Processing of the overlapping write requests during the merge operation may manifest as partial overwrites of one or more existing extents which, in turn, may result in logical storage space being trapped in the extent store.

Abstract: A system can maintain multiple queues for deduplication requests of different priorities. The system can also designate priority of storage units. The scheduling priority of a deduplication request is based on the priority of the storage unit indicated in the deduplication request and a trigger for the deduplication request.

Abstract: A system can maintain multiple queues for deduplication requests of different priorities. The system can also designate priority of storage units. The scheduling priority of a deduplication request is based on the priority of the storage unit indicated in the deduplication request and a trigger for the deduplication request.

Abstract: The embodiments described herein are directed to an organization of metadata managed by a volume layer of a storage input/output (I/O) stack executing on one or more nodes of a cluster. The metadata managed by the volume layer, i.e., the volume metadata, is illustratively embodied as mappings from addresses, i.e., logical block addresses (LBAs), of a logical unit (LUN) accessible by a host to durable extent keys maintained by an extent store layer of the storage I/O stack. In an embodiment, the volume layer organizes the volume metadata as a mapping data structure, i.e., a dense tree metadata structure, which represents successive points in time to enable efficient access to the metadata.

Abstract: A technique preserves efficiency for replication of data between a source node of a source cluster (“source”) and a destination node of a destination cluster (“destination”) of a clustered network. Replication in the clustered network may be effected by leveraging global in-line deduplication at the source to identify and avoid copying duplicate data from the source to the destination. To ensure that the copy of the data on the destination is synchronized with the data received at the source, the source creates a snapshot of the data for use as a baseline copy at the destination. Thereafter, new data received at the source that differs from the baseline snapshot are transmitted and copied to the destination. In addition, the source and destination nodes negotiate to establish a mapping of name-to-data when transferring data (i.e., an extent) between the clusters.

Abstract: A technique improves efficiency of a copy-on-write (COW) operation used to create a snapshot and/or clone by a volume layer of a storage input/output (I/O) stack executing on one or more nodes of a cluster. The snapshot/clone may be represented as an independent volume, and embodied as a respective read-only copy (snapshot) or read-write copy (clone) of a parent volume. Volume metadata managed by the volume layer is organized as one or more multi-level dense tree metadata structures, wherein each level of the dense tree includes volume metadata entries for storing the metadata. The volume metadata entries may be organized as metadata pages having associated metadata page keys. Each metadata page is rendered distinct or “unique” from other metadata pages in an extent store layer of the storage I/O stack through the use of a multi-component uniqifier contained in a header of each metadata page.

Abstract: A snap restore technique efficiently restores snapshots of storage containers served by a storage input/output (I/O) stack executing on one or more nodes of a cluster. A Small Computer Systems Interface administration layer interacts with a volume layer of the storage I/O stack to manage and implement a snap restore procedure to restore one or more snapshots of a storage container. The storage container may be a logical unit (LUN) embodied as parent volume (active volume) and the snapshot may be represented as an independent volume embodied as read-only copy of the active volume. The snap restore procedure may be configured to allow restoration to a single snapshot of a LUN or restoration of a plurality of LUNs organized as a consistency group from a group of snapshots.

Abstract: A technique efficiently creates a snapshot for a logical unit (LUN) served by a storage input/output (I/O) stack executing on a node of a cluster that organizes data as extents referenced by keys. In addition, the technique efficiently creates one or more snapshots for a group of LUNs organized as a consistency group (CG) and served by storage I/O stacks executing on a plurality of nodes of the cluster. To that end, the technique involves a plurality of indivisible operations (i.e., transactions) of a snapshot creation workflow administered by a Storage Area Network (SAN) administration layer (SAL) of the storage I/O stack in response to a snapshot create request issued by a host.

Abstract: Embodiments herein are directed to efficient crash recovery of persistent metadata managed by a volume layer of a storage input/output (I/O) stack executing on one or more nodes of a cluster. Volume metadata managed by the volume layer is organized as a multi-level dense tree, wherein each level of the dense tree includes volume metadata entries for storing the volume metadata. When a level of the dense tree is full, the volume metadata entries of the level are merged with the next lower level of the dense tree. During a merge operation, two sets of generation IDs may be used in accordance with a double buffer arrangement: a first generation ID for the append buffer that is full (i.e., a merge staging buffer) and a second, incremented generation ID for the append buffer that accepts new volume metadata entries. Upon completion of the merge operation, the lower level (e.g., level 1) to which the merge is directed is assigned the generation ID of the merge staging buffer.

Abstract: Embodiments herein are directed to efficient crash recovery of persistent metadata managed by a volume layer of a storage input/output (I/O) stack executing on one or more nodes of a cluster. Volume metadata managed by the volume layer is organized as a multi-level dense tree, wherein each level of the dense tree includes volume metadata entries for storing the volume metadata. When a level of the dense tree is full, the volume metadata entries of the level are merged with the next lower level of the dense tree. During a merge operation, two sets of generation IDs may be used in accordance with a double buffer arrangement: a first generation ID for the append buffer that is full (i.e., a merge staging buffer) and a second, incremented generation ID for the append buffer that accepts new volume metadata entries. Upon completion of the merge operation, the lower level (e.g., level 1) to which the merge is directed is assigned the generation ID of the merge staging buffer.

Abstract: A system includes a low pass-filter and a Savitzky-Golay filter. The low-pass filter receives and processes a first electrocardiogram signal. The filter removes at least the high frequency components of the first electrocardiogram signal. The Savitzky-Golay filter estimates a baseline variation of the first electrocardiogram signal from the filtered first electrocardiogram signal. Related apparatus, systems, techniques and articles are also described.

Abstract: In one embodiment, a node coupled to one or more storage devices executes a storage input/output (I/O) stack having a volume layer, a persistence layer and an administration layer that interact to create a copy of a parent volume associated with a storage container on the one or more storage devices. A copy create start message is received at the persistence layer from the administration layer. The persistence layer ensures that dirty data for the parent volume is incorporated into the copy of the parent volume. New data for the parent volume received at the persistence layer during creation of the copy of the parent volume is prevented from incorporation into the copy of the parent volume. A reply to the copy create start message is sent from the persistence layer to the administration layer to initiate the creation of the copy of the parent volume at the volume layer.

Abstract: The embodiments described herein are directed to efficient merging of metadata managed by a volume layer of a storage input/output (I/O) stack executing on one or more nodes of a cluster. The metadata managed by the volume layer, i.e., the volume metadata, is illustratively organized as a multi-level dense tree metadata structure, wherein each level of the dense tree metadata structure (dense tree) includes volume metadata entries for storing the volume metadata. The volume metadata entries of an upper level of the dense tree metadata structure are merged with the volume metadata entries of a next lower level of the dense tree metadata structure when the upper level is full. The volume metadata entries of the merged levels are organized as metadata pages and stored as one or more files on the SSDs.

Abstract: According to one or more embodiments of the present invention, a network cache intercepts data requested by a client from a remote server interconnected with the cache through one or more wide area network (WAN) links (e.g., for Wide Area File Services, or “WAFS”). The network cache stores the data and sends the data to the client. The cache may then intercept a first write request for the data from the client to the remote server, and determine one or more portions of the data in the write request that changed from the data stored at the cache (e.g., according to one or more hashes created based on the data). The network cache then sends a second write request for only the changed portions of the data to the remote server.

Abstract: A three-way merge technique efficiently updates metadata in accordance with a three-way merge operation managed by a volume layer of a storage input/output (I/O) stack executing on one or more nodes of a cluster. The metadata is embodied as mappings from logical block addresses (LBAs) of a logical unit (LUN) accessible by a host to durable extent keys, and is organized as a multi-level dense tree. The mappings are organized such that a higher level of the dense tree contains more recent mappings than a next lower level, i.e., the level immediately below. The three-way merge operation is an efficient (i.e.

Abstract: A technique for eliminating duplicate data is provided. Upon receipt of a new data set, one or more anchor points are identified within the data set. A bit-by-bit data comparison is then performed of the region surrounding the anchor point in the received data set with the region surrounding an anchor point stored within a pattern database to identify forward/backward delta values. The duplicate data identified by the anchor point, forward and backward delta values is then replaced in the received data set with a storage indicator.

Abstract: The embodiments described herein are directed to an organization of metadata managed by a volume layer of a storage input/output (I/O) stack executing on one or more nodes of a cluster. The metadata managed by the volume layer, i.e., the volume metadata, is illustratively embodied as mappings from addresses, i.e., logical block addresses (LBAs), of a logical unit (LUN) accessible by a host to durable extent keys maintained by an extent store layer of the storage I/O stack. In an embodiment, the volume layer organizes the volume metadata as a mapping data structure, i.e., a dense tree metadata structure, which represents successive points in time to enable efficient access to the metadata.

Abstract: A deferred refcount update technique efficiently frees storage space for metadata (associated with data) to be deleted during a merge operation managed by a volume layer of a node. The metadata is illustratively volume metadata embodied as mappings from logical block addresses (LBAs) of a logical unit (LUN) to extent keys maintained by an extent store layer of the node. One or more requests to delete (or overwrite) an LBA range within a LUN may be captured as page keys associated with metadata pages during the merge operation and the storage space associated with those metadata pages may be freed in an out-of-band fashion. The page keys of the metadata pages may be persistently recorded in a reference count (refcount) log to thereby allow the merge operation to complete without resolving deletion of the keys. A batch of page keys may be organized as one or more delete requests and, once the merge completes, the keys may be inserted into the refcount log.

Abstract: Systems for deduplicating one or more storage units of a storage system provide a scheduler, which is operable to select at least one storage unit (e.g. a storage volume) for deduplication and perform a deduplication process, which removes duplicate data blocks from the selected storage volume. The systems are operable to determine the state of one or more storage units and manage deduplication requests in part based state information. The system is further operable to manage user generated requests and manage deduplication requests in part based on user input information. The system may include a rules engine which prioritizes system operations including determining an order in which to perform state-gathering information and determining an order in which to perform deduplication. The system is further operable to determine the order in which storage units are processed.