I have a case open for this with Nutanix Support, however, while I'm waiting...
I'm wondering if anyone can explain why in a block that contains 12HDDs and 6SSDs (3-node block), only shows disk statistics for the SSDs and no values for the HDDs in the list (all metrics are 0).
Best answer by patrbng
From the Nutanix bible.... Your SSD's are not full enough for ILM to kick in and move capacity to the HDD's.
The other case is when the overall tier utilization breaches a specific threshold [curator_tier_usage_ilm_threshold_percent (Default=75)] where DSF ILM will kick in and as part of a Curator job will down-migrate data from the SSD tier to the HDD tier. This will bring utilization within the threshold mentioned above or free up space by the following amount [curator_tier_free_up_percent_by_ilm (Default=15)], whichever is greater. The data for down-migration is chosen using last access time. In the case where the SSD tier utilization is 95%, 20% of the data in the SSD tier will be moved to the HDD tier (95% –> 75%).