Symptoms
Using Unisphere for PowerMax 9.2.x or 10.x, against an array running 5978, the SG Demand Report appears to be double-counting physical used capacity when a host SG has an associated snapshot link.With Unisphere 10.x against a PowerMax V4 running 6079, it does not show the same and reporting is accurate.
Cause
The cause of this discrepancy is as designed. The allocated capacity on the output is not a physical capacity. It is a logical capacity and it is shown in such a way.The link target device is using this logical capacity at the time that the device is linked, but there is no physical capacity used due to array’s technologies to minimize physical used capacity.In 10.0, it was introduced the concept of effective capacity to replace allocated. We have effective which represents part of logical capacity which creates demand on array resources for effective capacity and user data which represent all logical use capacity.When using 10.0 against v3 array effective capacity is total logical capacity the same as it appears as allocated in 9.2.
Resolution
With Unisphere for PowerMax 9.2, would need to add the capacities to not include the "linked" storage groups, from the demand report. Could also use CLI commands to filter out the linked storage groups with sed, grep, awk or whatever preference.Using Unisphere for PowerMax 10, you have additional filtering that can help. If using the default link created SG's that contains "LNK", it is suggested to exclude these in the reports. Ex: Storage NotContain "LNK"
