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Why is there a mismatch between CLI and OSM for cluster aggregate capacity

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Applies to

  • ONTAP System Manager 9.6+ (OSM) New Experience
  • Aggregate capacity

Questions

  • Why is there a mismatch between CLI and System Manager for cluster and aggregate capacity?
  • Why does System Manager dashboard report less available space than expected compared to CLI?

Answer

  • The issue is visible when deduplication and compression are present
  • The used capacity is all the logical space that is used
  • The available space is physical space

Logical Physical space New Experience cluster and aggregate capacity

  • Deduplication and compression of the physical space that is left cannot be calculated
Logical Space
  • Logical space refers to how theoretical space may be used without taking into account things like deduplication or compression
    • Compression reduces the amount of physical storage required for a volume by combining data blocks in compression groups, each of which is stored as a single block
    • Data deduplication is a process that eliminates excessive copies of data and significantly decreases storage capacity requirements
Physical space 
  • Physical space refers to how many physical blocks are being used in data aggregates. This does not include:
    • Root aggregates
    • Spare disks
    • Parity disks
CLI output:
  • You can review more information with the following commands:

::> storage aggregate show
::> aggr show-space
::> aggr show -fields physical-used,data-compaction-space-saved-percent,sis-space-saved-percent,composite-capacity-tier-used,size,physical-used-percent,data-compaction-space-saved,sis-space-saved

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