Abstract: A technique protects user data within a storage system. The technique involves, in response to a request signal that directs the storage system to store the user data, generating first parity and second parity based on the user data. The technique further involves storing the first parity and the user data in a data uber of the storage system, the data uber providing redundant array of independent disks (RAID) protection. The technique further involves storing the second parity in designated free storage of the storage system, the designated free storage being separate from the data uber.

Abstract: A technique garbage collects user data within a storage system. The technique involves, in response to a request signal that directs the storage system to garbage collect user data, coalescing first user data and second user data to form new user data. The technique further involves generating first parity and second parity based on the new user data. The technique further involves storing the first parity and the new user data in a data uber of the storage system, the data uber providing redundant array of independent disks (RAID) protection. The technique further involves storing the second parity in designated free storage of the storage system, the designated free storage being separate from the data uber.

Abstract: In at least one embodiment, processing can include receiving a metadata (MD) update for a MD page, wherein the MD update has an associated type; determining whether the type is a custom MD type; responsive to determining the type is a custom MD type, performing first processing including: determining a custom bucket handle for the MD update based at least in part on the type and a logical index (LI) uniquely identifying the MD page; and applying the MD update to a custom bucket associated with the custom bucket handle; and responsive to determining the type is a custom MD type, performing second processing including: determining a regular bucket handle for the MD update based at least in part on the LI of the MD page; and applying the MD update to a regular bucket associated with the regular bucket handle.

Abstract: A method, computer program product, and computing system for processing, using a storage node, one or more updates to one or more metadata pages of a multi-node storage system. The one or more updates may be stored in one or more data containers in a cache memory system of the storage node, thus defining an active working set of data containers. Flushing ownership for each data container of the active working set may be assigned to one of the storage nodes based upon an assigned flushing ownership for each data container of a frozen working set and a number of updates within the frozen working set processed by each storage node, thus defining an assigned flushing storage node for each data container of the active working set. The one or more updates may be flushed, using the assigned flushing storage node, to a storage array.

Abstract: Techniques for reconstructing or building metadata pages in storage nodes that have a delta-log based architecture. The techniques include walking “up” an ancestor chain of a metadata page, detecting the most recent delta update for a metadata entry of the metadata page, writing the most recent delta update to a location of the metadata entry in the metadata page, setting a bitmap entry corresponding to the location of the metadata entry in the metadata page, detecting a less recent delta update for the metadata entry of the metadata page, and, having previously set the bitmap entry corresponding to the location of the metadata entry in the metadata page, avoiding writing the less recent delta update to the location of the metadata entry in the metadata page. In this way, the need to save in memory the entire ancestor chain of the metadata page can be eliminated.

Abstract: Data replication techniques can include receiving, at a source system, a write directed to a source logical device configured for asynchronous remote replication to a destination system; performing processing that flushes a transaction log entry for the write; and performing replication processing that uses a replication queue including a replication queue entry corresponding to the write that stores the first content to a logical address. The processing can create a replication log entry in a replication log for the write responsive to determining that the write is directed to the source logical device configured for asynchronous remote replication and that the first content has not been replicated. Responsive to the first content not being in cache, the first content can be retrieved using the reference to a storage location storing the first content. The reference can be obtained from the replication log entry or the replication queue entry.

Abstract: A system can use non-volatile solid state drives (SSDs) to provide storage. The SSDs can implement internal log structured systems (LSSs). A reversible write operation can be serviced by an SSD to write first data to an SSD logical address. The reversible write operation can update the SSD logical address to store the first data rather than old data stored at the SSD logical address prior to servicing the reversible write operation. The old data can be stored at an SSD physical address and mapping information indicates the SSD logical address is mapped to the SSD physical address. Servicing the reversible write operation can include: retaining the mapping information and the old data; and adding second mapping information that maps the SSD logical address to a second SSD physical address storing the first data. A subsequent read operation can read the old data using the retained mapping information.

Abstract: A method, computer program product, and computing system for executing a plurality of IO traces on a storage system. At least one vertical flow and at least one horizontal flow associated with the at least one vertical flow may be defined for the plurality of IO traces. A hierarchical representation of the plurality of IO traces may be generated with the at least one vertical flow and the at least one horizontal flow associated with the at least one vertical flow defined for the plurality of IO traces.

Abstract: A method, computer program product, and computing system for defining a normal IO write mode for writing data to a storage system, the normal IO writing mode including: writing the data to a cache memory system, writing the data to a journal, in response to writing the data to the journal, sending an acknowledgment signal to a host device, and writing the data from the cache memory system to a storage array. A request may be received to enter a testing IO write mode. In response to receiving the request, the data may be written to the cache memory system. The writing of the data to the journal may be bypassed. The acknowledgment signal may be sent to the host device in response to writing the data to the cache memory system. The data may be written from the cache memory system to the storage array.

Abstract: A method, computer program product, and computing system for defining a normal IO write mode for writing data to a storage system including: writing the data to a cache memory system of a first storage node, writing the data to a journal of the first storage node, sending a notification concerning the data to a second storage node, writing one or more metadata entries concerning the data to a journal of the second storage node, sending an acknowledgment signal to the host device, and writing the data to the storage array. A request may be received to enter a testing IO write mode. In response to receiving the request, the data may be written to the cache memory system. The writing of the data to the journal may be bypassed. The acknowledgment signal may be sent to the host device. The data may be written to the storage array.

Abstract: Techniques described herein coordinate inline deduplication among nodes in a storage system. The method includes storing, in a page descriptor ring on a node, data and a fingerprint associated with the data in an entry. The method includes determining that a flushing work set (FWS) has been frozen. The node identifies, in the page descriptor ring, entries associated with the frozen FWS and having fingerprints with a parity associated with the node. The node deduplicates the entries based on a fingerprint database on the node. The node synchronizes deduplication of the frozen FWS with a peer node, so as to receive deduplication results concerning entries having fingerprints with a parity associated with the peer node. The node replaces entries in the page descriptor ring with the deduplication results from the peer node, and flushes entries in the frozen FWS to a storage device.

Abstract: Techniques for providing dependency resolution for lazy snapshots in a storage cluster with a delta log-based architecture. The techniques include creating a dependency relationship between a parent metadata page and a child metadata page, receiving one or more new delta updates of the parent metadata page, and writing, to a metadata delta log, the new delta updates of the parent metadata page as specialized delta update entries that preserve or maintain the new delta update values and their corresponding original (old) delta update values. By preserving or maintaining both the new delta update values and the corresponding old delta update values of the parent metadata page in the metadata delta log, constraints pertaining to the order of de-staging the delta updates of the parent and child metadata pages can be reduced.

Abstract: Nodes in a storage system can autonomously ingest I/O requests and flush data to storage. First and second nodes determine a sequence separator, the sequence separator corresponding to an entry in a page descriptor ring that separates two flushing work sets (FWS). The first node receives an input/output (I/O) request and allocates a sequence identification (ID) number to the I/O request. The first node determines a FWS for the I/O request based on the sequence separator and the sequence ID number, and commits the I/O request using the sequence ID number. The I/O request and the sequence ID number are sent to the second node.

Abstract: Techniques described herein coordinate inline deduplication among nodes in a storage system. The method includes storing, in a page descriptor ring on a node, data and a fingerprint associated with the data in an entry. The method includes determining that a flushing work set (FWS) has been frozen. The node identifies, in the page descriptor ring, entries associated with the frozen FWS and having fingerprints with a parity associated with the node. The node deduplicates the entries based on a fingerprint database on the node. The node synchronizes deduplication of the frozen FWS with a peer node, so as to receive deduplication results concerning entries having fingerprints with a parity associated with the peer node. The node replaces entries in the page descriptor ring with the deduplication results from the peer node, and flushes entries in the frozen FWS to a storage device.

Abstract: A technique for scheduling access to a resource arranges tasks into multiple classes, where each class has a respective share and a respective priority. The share of a class sets an amount of access allocated to the class, and the priority sets an order in which the class can use its share, with higher priority classes getting access before lower-priority classes. The technique assigns latency-critical tasks, such as synchronous I/O tasks, to a first class having the highest priority and assigns bandwidth-critical tasks, such as background I/O processing, to a second class having a lower priority.

Abstract: In at least one embodiment, processing can include receiving a metadata (MD) update for a MD page, wherein the MD update has an associated type; determining whether the type is a custom MD type; responsive to determining the type is a custom MD type, performing first processing including: determining a custom bucket handle for the MD update based at least in part on the type and a logical index (LI) uniquely identifying the MD page; and applying the MD update to a custom bucket associated with the custom bucket handle; and responsive to determining the type is a custom MD type, performing second processing including: determining a regular bucket handle for the MD update based at least in part on the LI of the MD page; and applying the MD update to a regular bucket associated with the regular bucket handle.

Abstract: A method is used for uninterrupted data flushing in a storage system. An input/output (I/O) request is received. A pointer for a filling flushing work set (FWS) is atomically switching. A copy of the pointer for the filling FWS is saved, and the counter associated with a FWS referenced by the saved copy of the pointer is incremented. The saved copy of the pointer and the pointer for the filling FWS are compared, and upon determining that the saved copy of the pointer and the pointer for the filling are FWS equal, the I/O request is committed to a page descriptor ring and the counter associated with the FWS referenced by the saved copy of the pointer is decremented.

Abstract: An apparatus comprises at least one processing device that includes a processor coupled to a memory, and is configured to monitor latencies associated with processing of input-output operations in a plurality of storage nodes of a distributed storage system, to detect an unbalanced condition between the storage nodes based at least in part on the monitored latencies, and responsive to the detected unbalanced condition, to adjust an assignment of slices of a logical address space of the distributed storage system to the storage nodes. Adjusting the assignment of slices of the logical address space of the distributed storage system to the storage nodes responsive to the detected unbalanced condition illustratively comprises increasing a number of the slices assigned to one or more of the storage nodes having relatively low latencies and decreasing a number of slices assigned to one or more of the storage nodes having relatively high latencies.

Abstract: A method is used for uninterrupted data flushing in a storage system. A barrier in a page descriptor ring is determined to distinguish between a filling flushing work set (FWS) and a frozen FWS. A sequence number of an I/O request is compared to the barrier. A FWS corresponding to the I/O request is identified based on the comparison. The I/O request is committed to the identified FWS.

Abstract: A method, computer program product, and computer system for obtaining, by a computing device, one or more pages from a log to complete a write transaction. Parity of a line in a multi-line physical layer block may be calculated. The one or more pages may be written to the line in the multi-line physical layer block. The parity to the line may be written in the multi-line physical layer block. A bitmap associated with the physical layer block may be updated based upon, at least in part, writing the one or more pages and the parity to the line in the multi-line physical layer block.