Dell PowerFlex 4.6.x Install and Upgrade Guide

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Fine granularity layout performance considerations

Fine granularity layout enables 4 KB granularity and compression.

Table 1. Layout and performance considerationsThis table describes fine granularity and medium granularity layout performance considerations.
Fine granularity	Medium granularity
The benefit of the more efficient fine granularity data layout in storage pools, that allows 4 KB granularity plus compression.	In contrast to 1 MB granularity in medium granularity data layout, comes at some performance cost.
In most cases fine granularity is slower than medium granularity. When compression is enabled, reads are about 20% slower than in cases where compression is disabled. There are exceptions to these rules. For example, a small I/O write response time is similar in fine granularity and medium granularity.	Faster than fine granularity.
Snapshots have no impact on the performance of applications and workloads running during the snapshot creation	Snapshots might have an impact on performance in some cases. In cases that are very sensitive to performance and do not require snapshots, medium granularity would be a better choice. It would also be a good option for cases where the data cannot be compressed, as it may already be compressed, or if the data is encrypted by the application.

In cases that are very sensitive to performance and do not require snapshots, medium granularity would be a better choice. It would also be a good option for cases where the data cannot be compressed, as it may already be compressed, or if the data is encrypted by the application.

See the Increase SDS threads topic for details about increasing SDS threads for better performance in related information. For best performance, it is recommended to increase the number of SDS threads from eight to twelve when the CPUs have twelve or more physical cores.

NOTE:Increasing the SDS threads is expected to improve performance in cases where the CPU is bound; for example: small I/Os or fine granularity layout. In cases where performance is limited by drive performance (too few drives) or by the network (usually large I/Os), changing the number of SDS threads does not help.