FreeNAS 11.2 U6
(Bug exists as early as FreeNAS 9.x series)
Forum post for reference:
Reddit post, shows bug has existed for a while:
Detatching a pool permanently deletes all associated periodic snapshot tasks.
How to recreate:
1) Have as many Periodic Snapshot Tasks created for pools and datasets.
2) Detach any pool, regardless of number of vdevs or mirror/RaidZ, regardless if SSD, HDD, or external USB.
3) Observe that the Periodic Snapshot Tasks for this recently detached pool are missing.
4) Re-attach the same pool, expecting the Periodic Snapshot Tasks to reload.
5) Instead observe that they do not reappear, as they have been deleted permanently.
* This can also cause issues with snapshots' lifetime, such as "Keep for 3 months" or "Keep for 2 weeks".