What is the name of the drive sub-assembly which contains the platters and read/write heads?

A.
ATA

B.
SATA

C.
HDA

D.
IDE

Explanation:
Disk Drive Components

The key components of a hard disk drive are platter, spindle, read-write head, actuator arm
assembly, and controller board. I/O operations in a HDD is performed by rapidly moving the arm
across the rotating flat platters coated with magnetic particles. Data is transferred between the
disk controller and magnetic platters through the read-write (R/W) head which is attached to the
arm. Data can be recorded and erased on magnetic platters any number of times.
Platter: A typical HDD consists of one or more flat circular disks called platters. The data is
recorded on these platters in binary codes (0s and 1s). The set of rotating platters is sealed in a
case, called Head Disk Assembly (HDA). A platter is a rigid, round disk coated with magnetic
material on both surfaces (top and bottom). The data is encoded by polarizing the magnetic area,
or domains, of the disk surface. Data can be written to or read from both surfaces of the platter.
The number of platters and the storage capacity of each platter determine the total capacity of the
drive.
Spindle: A spindle connects all the platters and is connected to a motor. The motor of the spindle
rotates with a constant speed. The disk platter spins at a speed of several thousands of
revolutions per minute (rpm). Common spindle speeds are 5,400 rpm, 7,200 rpm, 10,000 rpm, and
15,000 rpm. The speed of the platter is increasing with improvements in technology; although, the
extent to which it can be improved is limited.
Read/Write Head: Read/Write (R/W) heads, read and write data from or to platters. Drives have
two R/W heads per platter, one for each surface of the platter. The R/W head changes the
magnetic polarization on the surface of the platter when writing data. While reading data, the head
detects the magnetic polarization on the surface of the platter. During reads and writes, the R/W
head senses the magnetic polarization and never touches the surface of the platter. When the
spindle is rotating, there is a microscopic air gap maintained between the R/W heads and the
platters, known as the head flying height. This air gap is removed when the spindle stops rotating
and the R/W head rests on a special area on the platter near the spindle. This area is called the
landing zone. The landing zone is coated with a lubricant to reduce friction between the head and
the platter. The logic on the disk drive ensures that heads are moved to the landing zone before
they touch the surface. If the drive malfunctions and the R/W head accidentally touches the
surface of the platter outside the landing zone, a head crash occurs. In a head crash, the magnetic
coating on the platter is scratched and may cause damage to the R/W head. A head crash
generally results in data loss.
Actuator Arm Assembly: R/W heads are mounted on the actuator arm assembly, which positions
the R/W head at the location on the platter where the data needs to be written or read. The R/W
heads for all platters on a drive are attached to one actuator arm assembly and move across the
platters simultaneously.
Drive Controller Board: The controller is a printed circuit board, mounted at the bottom of a disk
drive. It consists of a microprocessor, internal memory, circuitry, and firmware. The firmware
controls the power to the spindle motor and the speed of the motor. It also manages the
communication between the drive and the host. In addition, it controls the R/W operations by
moving the actuator arm and switching between different R/W heads, and performs the
optimization of data access.
EMC E10-001 Student Resource Guide. Module 2: Data Center Environment