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In Dell Unity OE version 4.2, host I/O limits were expanded to support vVols. vVols support either an absolute limit or a density-based limit, defined by IOPS or IOPS per GB, respectively. Host I/O limits are supported on data vVols specifically, Host I/O limits cannot be applied to config, swap, or memory vVols. While the implementation of host I/O limits is the same for vVols and block resources, the management of vVol host I/O limits is done entirely through VMware vSphere. Host I/O limits can be created in vSphere as a rule for a storage policy and then assigned at either the VM or vVol level. Unisphere can be used to monitor the vVol rate limiting, with the capability to display any I/O limits associated with the vVol, and real-time performance metrics, as shown in Figure 18.
In order to create a host I/O limit, when creating a VM storage policy, ensure that the field Rules based on data services field is set to EMC.UNITY.VVOL. Then, select I/O Limit as a new rule, and the configuration options for the I/O limit will be presented, as listed below. I/O limits can be created as either an absolute or density-based limit.
Host I/O limits can be configured within the same VM storage policy as the other capabilities, which are explained in the section VM storage policies. Host I/O limits are compatible with any Dell Unity vVol datastore, and no additional configuration is needed on the Dell Unity side to support this feature. Any Virtual Volumes which have a VM storage policy applied to them will be subject to the I/O limit defined in the VM storage policy, if it exists. Find more information about creating, applying, and managing VM storage policies in the section VM storage policies.