Dell Products Inc.

Vikram A Prabhakar

Vamsi K Vankamamidi

Socheavy D Heng

Jason E Raff

Mayank Ajmera

Geng Han

Ashok Tamilarasan

David Bernard

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.

Tracking writes and snapshot creation/deletion in memory to improve asynchronous replication performance and support lower recovery point objectives (RPOs)

Techniques can include: receiving, at a first node, a read I/O directed to a logical address; determining that the first node does not own the logical address; sending over an interconnect a redirect request from the first node to a second node that owns the first logical address; and the second node performing processing including: determining, in accordance with one or more criteria, whether the interconnect is overloaded; responsive to determining that the interconnect is not overloaded, sending a redirect reply over the interconnect to the first node where the redirect reply includes first content stored at the first logical address; and responsive to determining that the interconnect is overloaded, sending the redirect reply over the interconnect to the first node where the redirect reply includes physical location information identifying a first physical storage location or address on non-volatile storage of the first content of the first logical address.

I/O processing techniques in a multi-node system

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.

Servicing read requests

A method, computer program product, and computing system for receiving a metadata input/output (IO) request on a first storage node of a storage system. The metadata IO request may be partitioned into a plurality of metadata pages. The plurality of metadata pages may include a plurality of logical metadata pages and a plurality of virtual metadata pages. A family identifier may be obtained for each logical metadata page. The family identifier is a unique identifier assigned to a group of related metadata elements that share data, and is stored in a family identifier locking table. At least one of the plurality of metadata pages may be locked from access by a second storage node using the family identifier. The metadata IO request may be processed on the plurality of metadata pages by loading the at least one of the plurality of metadata pages into a memory of the first storage node.

System and method for managing metadata access locking in cache

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.

Managing caches using access information of cache pages

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.

Managing transient snapshots for reduced metadata writes

Techniques can include: configuring stretched volumes for asynchronous replication; specifying replication settings denoting selected replication service levels of asynchronous replication optimizations for the stretched volumes; performing asynchronous replication for the stretched volumes based on the replication settings; monitoring a current amount denoting an amount of a resource that is free and available for use; and responsive to determining that the current amount is below a minimum, performing a corrective action to increase the current amount, wherein the corrective action includes: changing a replication setting for a stretched volume from a first replication service level to a second replication service level, wherein the second replication service level is expected to consume less of the resource than the first replication service level when performing asynchronous replication for the stretched volume.

Techniques for dynamic resource balancing with asynchronous replication

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.

Managing locks in a transactional cache

In at least one embodiment, processing can include: receiving write operations; persistently recording, in a write cache or log, the write operations using page descriptors (PDESCs) of a PDESC pool and page buffers (PBs) of a PB pool; selecting, in accordance with criteria, write data pages stored in the PB pool for demotion to a physical large block (PLB) pool included in backend non-volatile storage, wherein each write data page selected denotes content written by a corresponding one of the write operations; responsive to the selecting, persistently storing the write data pages of the PB pool in the PLB pool; and updating PDESCs associated with the write data pages to reference corresponding storage locations in the PLB pool rather than in the PB pool.

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Apex, NC, United States of America

Vikram A Prabhakar