Abstract: A method, computer program product, and computing system for determining whether storage space usage on a storage system has reached a predefined threshold of a total storage capacity of the storage system. An out-of-space mode may be initiated on the storage system in response to determining that the storage space usage has reached the predefined threshold of the total storage capacity of the storage system. An amount of free storage capacity for exiting the out-of-space mode may be determined based upon, at least in part, a predefined minimum free storage capacity, a predefined maximum free storage capacity, and the total storage capacity of the storage system.

Abstract: A technique for managing a datapath of a data storage system includes receiving a request to access target data and creating a transaction that includes multiple datapath elements in a cache, where the datapath elements are used for accessing the target data. In response to detecting that one of the datapath elements is invalid, the technique further includes processing the transaction in a rescue mode. The rescue mode attempts to replace each invalid datapath element of the transaction with a valid version thereof obtained from elsewhere in the data storage system. The technique further includes committing the transaction as processed in the rescue mode.

Abstract: A method, computer program product, and computer system for receiving, by a computing device, new data to write to a leaf. At least two timestamps of the leaf may be examined. It may be determined whether a time interval between the at least two timestamps of the leaf is greater than an age threshold. The new data may be written to a first tier storage device when the time interval between the at least two timestamps of the leaf is less than the age threshold; The new data may be written to a second tier storage device when the time interval between the at least two timestamps of the leaf is greater than the age threshold.

Abstract: Dirty pages of cached user data are persistently stored to page buffers that are allocated from a page buffer pool in a persistent data storage resource of a data storage system, and are indicated by page descriptors that are stored at a head of a temporally ordered page descriptor ring as the dirty pages are stored to the page buffers. The disclosed technology performs a flush operation by selecting a work-set of non-sequential page descriptors within the page descriptor ring, flushing dirty pages from page buffers indicated by the page descriptors in the work-set to non-volatile data storage drives of the data storage system, and storing, for each one of the page buffers indicated by the page descriptors in the work-set, an indication that the page buffer is available for re-use.

Abstract: A method of managing storage space for a metadata consistency checking procedure (MCCP) is provided. The method includes (a) tracking an amount of metadata and an amount of user data organized by the metadata; (b) provisioning a quantity of storage dedicated to the MCCP based, at least in part, on a ratio of the amount of metadata to the amount of user data; and (c) upon initiation of the MCCP, building tracking structures within the provisioned storage dedicated to the MCCP. An apparatus, system, and computer program product for performing a similar method are also provided.

Abstract: Techniques for updating persistent statistics on a multi-transactional and multi-node storage system. The techniques can be practiced in a distributed storage system including a plurality of storage nodes. Each storage node can include a persistent storage configured to accommodate a set of delta counter pages, as well as a global counter page for summarizing delta count values tracked by respective delta counters. The techniques can include, in each storage node, tracking, by each of a set of delta counters, changes to delta count values due to storage node operations performed on units of data storage, and summarizing, periodically or at least at intervals, the delta count values of the respective delta counters as global count values. The techniques can further include summarizing the global count values across the respective storage nodes in a count summarization report and sending the count summarization report to a client via a communications interface.

Abstract: Techniques manage objects in data storage equipment. Such techniques involve receiving a request to create a new object for a particular object family (e.g., a collection of related data storage objects such as a production volume, snapshots, clones, snapshots of clones, etc.). Such techniques further involve deriving, for the particular object family, a total object count based on an active object count and a deleted object count for the particular object family. Such techniques further involve, in response to the request, performing an object management operation that (i) creates the new object when the total object count is less than a predefined total object count threshold and (ii) prevents creation of the new object when the total object count is not less than the predefined total object count threshold.

Abstract: A method of managing storage resources is provided. The method includes (a) storing data in an array of storage extents on respective storage drives of a plurality of storage drives, the array of storage extents having a first level of redundancy; and (b) in accordance with a storage management policy, adjusting the array of storage extents to have a second level of redundancy by changing the array of storage extents from having a first number of storage extents on respective storage drives to having a second number of storage extents on respective storage drives, the second level of redundancy providing a different tolerance for failure than the first level of redundancy. An apparatus, system, and computer program product for performing a similar method are also provided.

Abstract: A logical unit of non-volatile data storage is provided for persistently storing metadata. The logical unit is provided by allocating RAID (Redundant Array of Independent Disks) extents to the logical unit, and allocating logical block addresses for the logical unit from within a logical address space of the logical unit to store blocks of metadata written to the logical unit. In response to detecting that a stored indication of a last allocated logical block address for the logical unit has been lost, two RAID extents that were last allocated to the logical unit are identified, and a binary search is performed across logical block addresses within the two RAID extents that were last allocated to the logical unit to locate the last allocated logical block address for the logical unit within the logical address space of the logical unit.

Abstract: A method, computer program product, and computing system for allocating a first set of cores of a plurality of cores of a multicore central processing unit (CPU) for processing host input-output (IO) operations of a plurality of operations on a storage system. A second set of cores of the plurality of cores may be allocated for processing flush operations of the plurality of operations on the storage system. A third set of cores of the plurality of cores may be allocated for processing rebuild operations of the plurality of operations on the storage system. At least one of one or more host TO operations, one or more rebuild operations, and one or more flush operations may be processed, via the plurality of cores and based upon, at least in part, the allocation of the plurality of cores for processing the plurality of operations.

Abstract: A logical unit of non-volatile data storage is provided for persistently storing metadata. The logical unit is provided by allocating RAID (Redundant Array of Independent Disks) extents to the logical unit, and allocating logical block addresses for the logical unit from within a logical address space of the logical unit to store blocks of metadata written to the logical unit. In response to detecting that a stored indication of a last allocated logical block address for the logical unit has been lost, two RAID extents that were last allocated to the logical unit are identified, and a binary search is performed across logical block addresses within the two RAID extents that were last allocated to the logical unit to locate the last allocated logical block address for the logical unit within the logical address space of the logical unit.

Abstract: A method of managing storage space for a metadata consistency checking procedure (MCCP) is provided. The method includes (a) tracking an amount of metadata and an amount of user data organized by the metadata; (b) provisioning a quantity of storage dedicated to the MCCP based, at least in part, on a ratio of the amount of metadata to the amount of user data; and (c) upon initiation of the MCCP, building tracking structures within the provisioned storage dedicated to the MCCP. An apparatus, system, and computer program product for performing a similar method are also provided.

Abstract: A technique for performing data deduplication operates at sub-block granularity by searching a deduplication database for a match between a candidate sub-block of a candidate block and a target sub-block of a previously-stored target block. When a match is found, the technique identifies a duplicate range shared between the candidate block and the target block and effects persistent storage of the duplicate range by configuring mapping metadata of the candidate block so that it points to the duplicate range in the target block.

Abstract: A method of managing operation of a data storage system (DSS) is provided. The method includes (a) reserving space within a dedicated metadata storage region (DMSR); (b) in response to determining that accommodating a storage request requires use of the reserved space, entering a restricted write mode; (c) while operating in the restricted write mode, using the reserved space in a process that frees space within the DMSR outside the reserved space; and (d) exiting the restricted mode in response to freeing space within the DMSR outside the reserved space. An apparatus, system, and computer program product for performing a similar method are also provided.

Abstract: Techniques are directed to managing Redundant Array of Independent Disks (RAID) storage space. One technique involves providing, by RAID circuitry, a storage space request to mapper circuitry; receiving, by the RAID circuitry, a storage space reply from the mapper circuitry in response to the storage space request; and performing, by the RAID circuitry, a follow-up operation based on the storage space reply from the mapper circuitry. Another technique involves, receiving, by mapper circuitry, a storage space request from RAID circuitry; performing, by the mapper circuitry, a storage space management operation in response to the storage space request; and providing, by the mapper circuitry, a storage space reply to the RAID circuitry, the storage space reply identifying a result of the storage space management operation.

Abstract: A technique for managing user data in a storage system includes accessing RAID metadata to identify user data that the storage system backs with broken RAID arrays. The technique further includes marking metadata that points to at least some of that user data to identify such user data as uncorrectable.

Abstract: A method, computer program product, and computer system for identifying, by a computing device, a pattern in a super block of a logger tier. It may be determined that the pattern in the super block of the logger tier is a known pattern, wherein the known pattern indicates invalid data in the logger tier. The logger tier may be booted up by storing an unknown pattern in the super block into the logger tier, wherein the unknown pattern indicates valid data in the logger tier.

Abstract: A technique for managing user data in a storage system includes accessing RAID metadata to identify user data that the storage system backs with broken RAID arrays. The technique further includes marking metadata that points to at least some of that user data to identify such user data as uncorrectable.

Abstract: A data storage system in which a transaction is generated that indicates at least one data block of a logical volume to be written to non-volatile data storage of a data, and in which the logical volume is accessible to multiple nodes in the data storage system. A system-wide lock is obtained for each data block indicated by the transaction. A new generation identifier is then created that is equal to a last transaction identifier that was created and stored during processing of a previously completed transaction. Each data block indicated by the transaction is stored into the non-volatile data storage of the data storage system together with the new generation identifier and the last transaction identifier is updated before each system-wide lock on each data block indicated by the transaction is released.

Abstract: Techniques for rebuilding a failed drive of a plurality of drives are provided. The techniques include: (a) determining a number of empty data stripes that have been allocated from the plurality of drives; (b) applying a set of decision criteria to the determined number to yield a decision, wherein applying the set of decision criteria yields a first decision at a first time and a differing second decision at a second time; (c) in response to the first decision at the first time, deallocating an empty data stripe that was allocated from the plurality of drives to yield a plurality of data extents on disparate drives of the plurality of drives and continuing to rebuild the failed drive onto at least one of the plurality of data extents; and (d) in response to the second decision at the second time, pausing rebuilding the failed drive until applying the set of decision criteria yields the first decision.