How does FabricPool inactive data reporting work?

Block temperature

When a block is written to the local tier, it is assigned a temperature value indicating that it is hot. Over time, a background cooling scan cools blocks, making hot blocks warm and eventually turning blocks cold if they have not been read. Assuming no activity, a block becomes cold based on the time set by the tiering-minimum-cooling-days setting.

Inactive Data Reporting

• Once enabled, IDR monitors the underlying data access across a fixed 31-day cooling period to determine which data is considered cold  or inactive.
• Starting with ONTAP 9.8 the cooling period used by IDR can be adjusted for auto and snapshot-only tiering policies.

1. To verify that IDR is enabled on the aggregates, use the command storage aggregate show -fields is-inactive-data-reporting-enabled

::> storage aggregate show -fields is-inactive-data-reporting-enabled    
aggregate is-inactive-data-reporting-enabled
----------------- ----------------------------------
aggr0_cluster1_01 false
aggr0_cluster1_02 false
cluster1_01_SSD_1 false
cluster1_02_SSD_1 false
4 entries were displayed.

2. If IDR is not enabled, use the command storage aggregate modify -aggregate <aggr_name> -is-inactive-data-reporting-enabled true to turn on inactive data reporting. 

3. To display how much data is inactive on a volume, use the AutoSupport section VOLUME.XML or  volume show  command with the -fields performance-tier-inactive-user-data,performance-tier-inactive-user-data-percent parameter.

::> volume show -fields performance-tier-inactive-user-data,performance-tier-inactive-user-data-percent    

vserver volume performance-tier-inactive-user-data performance-tier-inactive-user-data-percent
------- ------ ----------------------------------- -------------------------------------------
vsim1 vol0 0B 0%
vs1 vs1rv1 0B 0%
vs1 vv1 10.34MB 0%
vs1 vv2 10.38MB 0%
4 entries were displayed.

• The performance-tier-inactive-user-data field displays the amount of inactive user data stored in the performance tier that could be tiered out to a cloud tier if the volume is in a FabricPool and for which the auto tiering policy has been specified
• The performance-tier-inactive-user-data-percent field displays what percent of the data is inactive across the active file system and Snapshot copies

4. To display how much data is stored in the performance and cloud tiers for FabricPool per volume you run the command  volume show-footprint  or use AutoSupport section  VOL-STATUS-F 

::> volume show-footprint -volume vol1

Vserver : SVM1
Volume : vol1

Feature Used Used%
-------------------------------- ---------------- -----    
Volume Data Footprint 183GB 1%
Footprint in Performance Tier 8.85GB 5%
Footprint in StorageAccount 174GB 95%
Flexible Volume Metadata 1.04GB 0%
Delayed Frees 28.8MB 0%

Total 184GB 1%