Abstract: Techniques for tracking incoming writes and snap creation/deletion in memory to improve asynchronous replication and support lower RPOs. In the techniques, a storage system uses its data cache to receive data specified in write requests issued by storage clients, while dedicating an amount of the cache memory to track and record offsets/lengths of writes directed to source volumes. At the end of each replication interval, the storage system obtains a list of the recorded offsets/lengths for each source volume, identifies and reads areas of the source volume that were written to during the replication interval using the list, and replicates data from the identified areas to a destination volume. Because the list of recorded offsets/lengths of incoming writes for the source volume is compiled and available from volatile cache memory, it can be generated and accessed very quickly using reduced processing/memory resources, allowing for lower RPOs in asynchronous replication processes.

Abstract: A technique is directed to servicing a read request. The technique includes establishing a set of write indicators corresponding to a set of storage locations designated by the read request. The technique further includes, while the set of write indicators is accessible to a possible write operation that designates the set of storage locations to be written to, buffering data from the set of storage locations. The technique further includes, after buffering the data from the set of storage locations, checking the set of write indicators to ascertain whether the set of storage locations has been designated to be written to since establishing the set of write indicators.

Abstract: Techniques for tracking incoming writes and snap creation/deletion in memory to improve asynchronous replication and support lower RPOs. In the techniques, a storage system uses its data cache to receive data specified in write requests issued by storage clients, while dedicating an amount of the cache memory to track and record offsets/lengths of writes directed to source volumes. At the end of each replication interval, the storage system obtains a list of the recorded offsets/lengths for each source volume, identifies and reads areas of the source volume that were written to during the replication interval using the list, and replicates data from the identified areas to a destination volume. Because the list of recorded offsets/lengths of incoming writes for the source volume is compiled and available from volatile cache memory, it can be generated and accessed very quickly using reduced processing/memory resources, allowing for lower RPOs in asynchronous replication processes.

Abstract: Improved techniques are directed to managing a cache in an electronic environment in which a first processing core is configured to utilize a first set of queues to reclaim the pages of the cache and a second processing core is configured to utilize a second set of queues to reclaim the pages of the cache. The techniques include adding, to a queue in the first set of queues, an entry identifying access information of a page of the cache. The techniques further include accessing the page by a second processing core. The techniques further include, while the entry is in the first set of queues, updating the access information by the second processing core to indicate accessing the page by the second processing core.

Abstract: A technique for managing transient snapshots identifies an instruction to create a transient snapshot with an indicator and attempts to delay, based on the indicator, flushing of the instruction from cache to a mapping subsystem at least until the cache receives an instruction to delete the transient snapshot.

Abstract: Improved techniques are directed to managing a cache in an electronic environment in which a first processing core is configured to utilize a first set of queues to reclaim the pages of the cache and a second processing core is configured to utilize a second set of queues to reclaim the pages of the cache. The techniques include adding, to a queue in the first set of queues, an entry identifying access information of a page of the cache. The techniques further include accessing the page by a second processing core. The techniques further include, while the entry is in the first set of queues, updating the access information by the second processing core to indicate accessing the page by the second processing core.

Abstract: A technique of managing locks in a transaction cache includes opening, in the transactional cache, a first transaction identifying a first plurality of pages to be accessed and a second transaction identifying a second plurality of pages to be accessed, where the first plurality of pages has at least one page in common with the second plurality of pages. The technique further includes selecting a target page that is highest in a predefined page ordering out of the at least one page in common. The second plurality of pages includes a lower-ordered page that is lower in the predefined page ordering than the target page. The technique further includes, while the first transaction is open, inserting a first lock request of the second transaction into a queue of the target page and preventing insertion of a second lock request of the second transaction into a queue of the lower-ordered page.

Abstract: A technique for managing transient snapshots identifies an instruction to create a transient snapshot with an indicator and attempts to delay, based on the indicator, flushing of the instruction from cache to a mapping subsystem at least until the cache receives an instruction to delete the transient snapshot.

Abstract: A technique of managing locks in a transaction cache includes opening, in the transactional cache, a first transaction identifying a first plurality of pages to be accessed and a second transaction identifying a second plurality of pages to be accessed, where the first plurality of pages has at least one page in common with the second plurality of pages. The technique further includes selecting a target page that is highest in a predefined page ordering out of the at least one page in common. The second plurality of pages includes a lower-ordered page that is lower in the predefined page ordering than the target page. The technique further includes, while the first transaction is open, inserting a first lock request of the second transaction into a queue of the target page and preventing insertion of a second lock request of the second transaction into a queue of the lower-ordered page.

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 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: Techniques for providing a cache-based mechanism for snapshot management and creation in a data storage system. The techniques include creating, in a cache memory, a snapshot of a data volume such that the same data is shared between the data volume and the snapshot, and modifying, in the cache memory, one or more data pages among a plurality of data pages of the data volume. The techniques further include maintaining, on a list in the cache memory, copies of the data pages of the snapshot previously shared with the data volume prior to their modification, and maintaining, in a table in the cache memory, a copy record that contains information describing the relationship between the data volume and the snapshot. The techniques still further include flushing, in log order, the data pages of the snapshot and the copy record of the data volume and the snapshot to a storage device.

Abstract: Techniques for providing a cache-based mechanism for snapshot management and creation in a data storage system. The techniques include creating, in a cache memory, a snapshot of a data volume such that the same data is shared between the data volume and the snapshot, and modifying, in the cache memory, one or more data pages among a plurality of data pages of the data volume. The techniques further include maintaining, on a list in the cache memory, copies of the data pages of the snapshot previously shared with the data volume prior to their modification, and maintaining, in a table in the cache memory, a copy record that contains information describing the relationship between the data volume and the snapshot. The techniques still further include flushing, in log order, the data pages of the snapshot and the copy record of the data volume and the snapshot to a storage device.