What inactive (cold) data is

Infrequently accessed data in a performance tier is known as inactive (cold) data. By default, data that is not accessed for a period of 31 days becomes inactive.

Inactive data is displayed at the aggregate level, cluster level, and volume level. The inactive data for an aggregate or a cluster is displayed only if inactive scanning is complete on that aggregate or cluster. By default, inactive data is displayed for FabricPool-enabled aggregates. If you want to view inactive data for SSD aggregates, you must manually enable inactive data.