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65 Dell EMC SC Series: Best Practices with VMware vSphere | 2060-M-BP-V
As shown in Figure 36, the default setting for the congestion threshold is 30 milliseconds of latency or 90
percent of peak throughput.
Setting the congestion threshold
As a best practice, leave this setting at default value unless under the guidance of VMware or Dell Support.
For more information about SIOC, refer to the vSphere Resource Management Guide at VMware vSphere
documentation, or the article, Unmanaged I/O workload detected on shared datastore running Storage I/O
Control (SIOC) for congestion management in the VMware Knowledge Base.
16.1.1 SIOC and volume QoS
Similar to VMware SIOC, SCOS 7.0 introduces the volume QoS feature, which allows array administrators to
limit bandwidth, IOPS, and prioritize storage workloads at the array level. While SIOC allows vSphere
administrators control over storage within the vSphere cluster, volume QoS can balance all array workloads
external to vSphere to prevent a noisy neighbor effect. Volume QoS allows all workloads within the array to
be balanced for fairness.
Before implementing volume QoS, refer to the guide Volume Quality of Service Best Practices with Dell SC
Series Storage.