The drive enclosure is the external casing of the hard disk drive. It provides features for mounting the drive in the drive bay of the host system, and supports other components of the HDD such as spindle motor, actuator, PCB etc. There are two parts of the enclosure - top cover and base plate. All components are assembled on the base plate.
Electronic components of an HDD can be categorized according to the following functions:
1. Electronics for reading/writing also known as the channel electronics.
2. Electronics for spinning the disks and positioning of the read/write head also known as the servo channel.
3. Electronics for controlling various operations (such as read data, write data, transfer data between HDD and host etc) of the disk or the disk controller.
4. Electronics for interface with the host system.