Hi Team, I am trying to move history partitions of my primary key table to HDD disks. I tried to 1: set storage cooldown time; 2: set storage medium; but the tablets are not migrated to HDD disk. How to figure out the reason? and is there a best practice of migrating history partitions?

You might want to use backup and restore. https://docs.starrocks.io/docs/administration/management/Backup_and_restore/#create-a-repository