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FlashArray//C VMware Managed Snapshot Performance

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For more information from VMware on this topic, check out their blog post on backup performance improvement recommendations.

Pure's FlashArray//C was introduced to provide a capacity-optimized storage platform.   FlashArray//X on the other hand, is a performance-optimized storage platform designed to provide the lowest I/O latency and highest IOPS performance.  When comparing the relative performance of FlashArray//X and FlashArray//C it should come as no surprise that most, if not all, latency-sensitive applications will be less performant on FlashArray//C.  The difference in average I/O latency becomes most pronounced in cases where single-threaded and low thread count read I/O are used on FlashArray//C.  In practical terms, it means being able to perform one read I/O every ~300 microseconds (//X) vs. one read I/O every ~3,500 microseconds (//C).  Such was the case with some VMware-managed snapshot operations on FlashArray//C prior to Purity version 6.1.9. 

All of the below tests were run on a VMFS6 datastore with individual snapshots that were less than 350 GB in size. For snapshot creation, about 7.5k write IOPS were run on the arrays to generate data for snapshots; for deletion, the arrays had no load other than the deletion operation. The tests were run on a single VM that was powered on for the duration of the testing.

For deleting all snapshots, there were 3 snapshots present with about 350 GB in total snapshot size reported by vCenter.

Test FlashArray//X50R2
Purity 6.1.10
FlashArray//C40R3
Purity 6.1.1
FlashArray//C40R3
Purity 6.1.10
vCenter manual snapshot creation 2 minutes or less 2 minutes or less 2 minutes or less
vCenter manual single snapshot deletion 8 Minutes 30 Minutes 9 Minutes
vCenter manual delete all snapshots 10 Minutes 56 Minutes 14 Minutes

Why is there a test duration difference between Purity versions for FA//C? 

Starting with Purity 6.1.9, a performance optimization was added to improve read latency for single-threaded I/O streams (like VMware-managed snapshot operations). As VMware's managed snapshot operations make use of low thread count and single-threaded read I/O, the duration of various snapshot activities (like consolidation, deletion) are heavily influenced by storage array read latency.  As FlashArray//C read latency for single-threaded operations had been 3.5-4ms prior to Purity version 6.1.9, the duration for these activities was also considerably longer than FlashArray//X which provides less than 1 ms read I/O latency.

VMware has a related KB article.

 

More information on VMware's snapshot deletion operations can be found in this VMware KB and on this VMware area page.