VNX Capacity Anomaly and Calculations (November 4, 2019)

Live Optics Agent

Overview

 

There is a known defect in a small percentage of VNX SP Collect .XML files where the data will render an impossible Used capacity value that is higher than the actual capacity in the array itself.

This issue is isolated to the Used Capacity and therefore the Free Capacity values. All other values are unaffected.

There is no known cause or remedy for this anomaly on the VNX array itself. It is associated with an undocumented and rare array configuration scenario. Re-running the collection is likely to yield the same results.

Live Optics will detect this anomaly and apply corrections that account for the data defects in the SP Collect .XML file. When successful, the report generates without a warning message.

In extremely rare scenarios the anomaly cannot be adjusted successfully.  

When this occurs, the Used Capacity would incorrectly show an impossible higher value than the Configured Capacity. In these circumstances, Live Optics will make the Used Capacity equal to the Configured Capacity.

In other words, the array is assumed to be fully utilized. A warning message and link to this article is provided to indicate the scenario. Live Optics has no further capabilities to normalize the data.

 

 Below are the calculations for the capacity section.

  • Configured Capacity
    Sum of all Raid Group capacity values. Excluding Unbound, Fast Cache and Hot Spares.
  • Used Capacity
    Sum of thin Pool LUNs Consumed Capacity Values + the sum of thick Pool LUNs Consumed Capacity values. Alternative formula: Pool consumed + Raid Group Consumed (only traditional RG LUNs).
  • Free Capacity
    Configured Capacity - Used Capacity.
  • Subscribed Capacity  
    Sum of RAID Group Capacity values + Sum of Pool LUNs User Capacity
  • RAID Group Free Capacity  
    Sum of RAID Group Free Capacity values. Excluding Unbound, Fast Cache and Hot Spares
  • RAID Group Capacity  
    Configured Capacity - RAID Group Free Capacity value
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