By using VMware vSphere Storage I/O Control, you can prioritize cluster-wide storage I/O for management workloads on the supplemental NFS storage in the management domain of VMware Cloud Foundation. As a result, workload consolidation is better and you can reduce extra costs associated with over-provisioning.

vSphere Storage I/O Control extends the constructs of shares and limits to storage I/O resources. Shares are set on a per-virtual machine basis. You can control the amount of storage I/O that is allocated to virtual machines during periods of I/O contention, so that more important virtual machines have greater access to the storage array for I/O resource allocation.

When vSphere Storage I/O Control is enabled on a datastore, the ESXi host monitors the device latency when communicating with that datastore. If the device latency exceeds a threshold, the datastore is considered congested and each virtual machine that accesses that datastore is allocated I/O resources according to their shares. vSphere Storage I/O Control has several requirements, limitations, and constraints.

  • Datastores that are enabled with vSphere Storage I/O Control must be managed by a single vCenter Server system.

  • Storage I/O Control is supported on supplemental NFS-connected storage with NFS version 3. You cannot use Storage I/O Control on datastores with NFS version 4.1.

  • Storage I/O Control is not applicable on principal vSAN datastores.

  • Storage I/O Control does not support datastores with multiple extents.

  • Before using vSphere Storage I/O Control on datastores that are backed by arrays with automated storage tiering capabilities, verify that the storage arrays have been certified as compatible with vSphere Storage I/O Control. See VMware Compatibility Guide.

Table 1. Design Decisions on Storage Policies and Controls

Decision ID

Design Decision

Design Justification

Design Implication


Enable Storage I/O Control with the default values on all supplemental NFS datastores.

Ensures that all virtual machines on a datastore receive equal amount of I/O capacity.

Virtual machines that use more I/O access the datastore with priority. Other virtual machines can access the datastore only when an I/O contention occurs on the datastore.