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Creating a local tier (aggregate) estimates usable size approximately 5% less than actual created size

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  • When creating a local tier (aggregate) ONTAP reports a Usable Size approximately 5% smaller than the actual Size of the aggregate once created:

cluster1::> storage aggregate auto-provision -nodes cluster1-01 -verbose true
Per node summary of new aggregates to create, discovered spares, and also
remaining spare disks and partitions after aggregate creation:

                     New    Total New Discovered Spare Remaining Spare
Node               Aggrs  Usable Size  Disks  Partitions  Disks Partitions
------------------ ----- ------------ ------ ----------- ------ ----------
cluster1-01            1      50.00TB     42           0      2          0

cluster1::> storage aggregate show -fields size -aggregate cluster1_01_SAS_1
aggregate            size
-------------------- -------
cluster1_01_SAS_1    52.78TB

  • As detailed in the ONTAP® 9 Release Notes the following enhancements were made:
    • For All Flash FAS (AFF) and the FAS500f platforms, the WAFL reserve for aggregates greater than 30TB is reduced from 10% to 5%, resulting in increased usable space in the aggregate.  Available beginning ONTAP 9.12.1.
    • For FAS platforms, the WAFL reserve for aggregates greater than 30TB in size is reduced from 10% to 5%, resulting in increased usable space in the aggregate.  Available beginning ONTAP 9.14.1.


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