When you enable Storage I/O Control, ESX/ESXi monitors datastore latency and adjusts the I/O load sent to it, if datastore average latency exceeds the threshold.
Procedure
1
Select a datastore in the vSphere Client inventory and click the Configuration tab.
2
Click Properties.
3
Under Storage I/O Control, select the Enabled check box.
4
Click Close.
On the Datastores tab, the Storage I/O Control column shows that Storage I/O Control is enabled for the datastore.