Dell Products Inc.

Kaustubh Sahasrabudhe

Ramesh Doddaiah

Malak Alshawabkeh

Steve Ivester

John Creed

Two storage arrays implement a Remote Data Replication (RDR) facility between a primary storage array and a backup storage array. The primary storage array collects global memory usage statistics by host processes on the primary array and global memory usage by the RDR process on the primary array. The backup storage array collects global memory usage statistics by host processes on the backup array and global memory usage by the RDR process on the backup array. The primary storage array transmits information about the global memory usage by the RDR process on the primary array to the backup array. The backup storage array transmits information about the global memory usage by the RDR process on the backup array to the primary array. Both arrays use global memory usage statistics by their respective local host process and the RDR process on both arrays, to locally set global memory segmentation policies.

Global memory segmentation adjustment

One or more aspects of the present disclosure relate to cache layout optimization. In embodiments, an input/output (IO) workload is received by a storage array. Further, cache slot allocations are dynamically adjusted for each cache segment of global memory based on one or more characteristics of the IO workload.

Cache layout optimization

A shared global memory segmentation conversion process optimizes conversion of shared Global Memory (GM) in connection with changes to a global memory segmentation policy. When a policy region is to be reduced in size, the GM banks of the policy region are ranked and one or more of the lowest performing GM banks in the policy region are selected to be moved to the other policy region. Similarly, within each policy region, IO pools, used to create slots of particular sizes, that are being reduced in size are determined, and the GM banks of the IO pools are ranked. One or more of the lowest performing GM banks are selected and moved to an IO pool that is being increased in size. This process iterates, re-ranking the remaining GM banks in the policy region/IO pools, until the correct allocation of GM policy regions and IO pools is achieved.

Global memory segmentation conversion

A random read miss slot size selection engine is configured to select between multiple memory slot sizes to optimize slot size allocations for random read miss IO operations. Upon receipt of an IO operation that is a random read miss IO operation, the slot size selection engine obtains a metadata page encompassing multiple entries in addition to an entry associated with the random read miss IO operation. The slot size selection engine performs a metadata temporal analysis to analyze temporal information associated with previous slot allocations identified in the metadata page. The slot size selection engine also performs a metadata spatial analysis to spatially analyze previous slot allocations to neighboring tracks identified in the metadata page. In response to a determination that the metadata page contains a threshold number of recent slot allocations, the spatial analysis is used to determine the slot size to allocate to the random read miss.

Optimal memory slot size selection for random read miss IO operations

A multi-node storage system uses local mutual exclusion to perform fabricless local memory access and non-local mutual exclusion to perform memory access via an inter-nodal fabric. A local access mode bit and remote access request flag are associated with each data slot and its associated metadata in shared memory of the storage system. Local mutual exclusion such as a Peterson Lock is used to avoid conflict between local IO threads when the local access mode is set and the remote access request flag is not set. A remote IO thread that determines that the local access mode bit for a target slot is set will set the remote access flag. In response, a local IO thread that obtains the Peterson Lock will unset the local access mode bit and release the Peterson Lock, thereby enabling remote access to the slot and its metadata by the remote IO thread. The remote access request flag is cleared and the local access mode enabled after the remote access is completed.

Atomic CPU access to shared metadata in a fabric-attached multi-node array with shared memory

Worker threads allocate at least some recycled cache slots of a local portion of a shared memory to the compute node to which the memory portion is local. More specifically, the recycled cache slots are allocated prior to receipt of the IO that the recycled cache slot will be used to service. The allocated recycled cache slots are added to primary queues of each compute node. If a primary queue is full then the worker thread adds the recycled cache slot, unallocated, to a secondary queue. Cache slots in the secondary queue can be claimed by any compute node associated with the shared memory. Cache slots in the primary queue can be used by the local compute node without sending test and set messages via the fabric that interconnects the compute nodes, thereby improving IO latency.

Fabricless allocation of cache slots of local shared caches with cache slot recycling in a fabric environment

A data storage node includes a plurality of compute nodes that allocate portions of local memory to a shared cache. The shared cache is configured with mirrored and non- mirrored segments that are sized as a function of the percentage of write IOs and read IOs in a historical traffic workload profile specific to an organization or storage node. The mirrored and non-mirrored segments are separately configured with pools of data slots. Within each segment, each pool is associated with same-size data slots that differ in size relative to the data slots of other pools. The sizes of the pools in the mirrored segment are set based on write IO size distribution in the historical traffic workload profile. The sizes of the pools in the non-mirrored segment are set based on read IO size distribution in the historical traffic workload profile.

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Westborough, MA, United States of America

Kaustubh Sahasrabudhe