You can destroy a pool even if the pool contains mounted datasets by using the zpool destroy pool command.
Caution - ZFS cannot always keep track of which devices are in use. Ensure that you are destroying the correct pool and you always have copies of your data. If you accidentally destroy the wrong pool, see Recovering Destroyed ZFS Storage Pools.
When you destroy a pool, the pool is still available for import. Therefore, confidential data might remain on the disks that were part of the pool. To completely destroy the data, use a feature like the format utility's analyze->purge option on every disk in the destroyed pool.
To ensure data confidentiality, create encrypted ZFS file systems. Even if a destroyed pool is recovered, the data would remain inaccessible without the encryption keys. For more information, see Encrypting ZFS File Systems.
When a pool with a mix of available and unavailable devices is destroyed, data is written to the available disks to indicate that the pool is no longer valid. This state information prevents the devices from being listed as a potential pool when you perform an import. Even with unavailable devices, the pool can still be destroyed. When the unavailable devices are repaired, they are reported as potentially active when you create a new pool and appear as valid devices when you search for pools to import.
A pool itself can become unavailable if a sufficient number of its devices are unavailable. The state of the pool's top-level virtual device is reported as UNAVAIL. In this case, you can destroy the pool only by using the zpool destroy –f command.
For more information about pool and device health, see Determining the Health Status of ZFS Storage Pools.