Your question sounds fairly straightforward but there are a few important factors. How you do this depends on the following
1) Version of OS that you have on the system
2) Whether your disks are unprotected, mirrored or RAID protected.
If you can let me know these bit of info, I can advise further.
(ex IBM hardware engineer)
The best way to remove the hard disk drive after cleaning or sanitizing, is to carefully remove all the connected wires or cables. Remember to avoid the drive from being fallen on the ground because it could cause a hardware failure which could make it totally unusable.