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Host I/O Limits is a feature of the PowerMax which allows users to place limits on the front-end bandwidth and IOPS consumed by applications on the array.
Limits are set on a per-storage-group basis. As users build masking views with these storage groups, limits for maximum front-end IOPS and/or MB/s are evenly distributed across the directors within the associated masking view. The bandwidth and IOPS are monitored by the array to ensure that they do not exceed the user-specified maximum.
The benefits of implementing Host I/O Limits are:
To configure the Host I/O Limits on a set of devices, a Host I/O Limit is added to a storage group. A masking view is then created using that storage group. This causes the Host I/O Limit defined on the storage group to be applied to the devices in the storage group for the ports included in the port group, as well as any child storage group(s). The Host I/O Limit for a storage group can be either active or inactive.
Note: In most cases, the total Host I/O Limit may only be achieved with proper host load balancing between directors by multipath software on the hosts such as PowerPath/VE.
The Host I/O Limit can be set using the SYMCLI command symsg or Unisphere. Figure 130 demonstrates the use of SYMCLI to set the Host I/O Limit.
Using Unisphere navigate to Storage Groups and select on one of them. This will bring up the properties of the storage group. Select Set Host I/O Limits, fill in the desired limit, by MB/sec or IO/sec or both, and hit “OK” as seen in Figure 131.
Host I/O Limits can also be set during provisioning. In the following example in Unisphere for PowerMax in Figure 132, two child storage groups are assigned different values, one will be limited by MB/s, the other by IO/s. Host I/O Limits can be changed at will or removed at any time.
For more information about Host I/O Limits please refer to the Technical Note available on https://www.dell.com/support/home/en-us.