Hard Disks

platters/disks

Every hard drive is a stack of high-speed spinning ____

magnetized metal grains

Each disk in a hard drive is coated with a film of microscopic _____

grains

In hard drives, data is recorded as a magnetic pattern formed by groups in tiny ___

bit

Each group in a hard drive is known as a __

0s and 1s

Two possible states of magnetized grains

electromagnet

Data is written onto the disc by converting strings of bits into electrical current fed through an _____

600

Areal density of a modern hard drive is about ___ gigabits per square inch

Moore’s Law

In 1975, scientists predicted that information density would double every two years

Superparamagnetic Effect

When a magnetic grain volume is too small, its magnetization is easily disturbed by heat energy and can cause bits to switch unintentionally, leading to data loss

longitudinal (horizontal), perpendicular (vertical)

Scientists changed the direction of recording in hard drive from ______ (____) to ______ (____)

HAMR

Uses focused laser to heat the region in a hard drive being written

Bit-patterned media

Bit locations are arranged in separate, nano-sized structures

Spindle

Holds one or more platters and spins in the hard disk

120 nm cobalt chromium tantalum alloy

The magnetic functional layer in hard disks

Voice coil

Enable hard disk arm stack assembly and read/write head to move back and forth

Ferromagnetic and non-magnetic materials

Materials inside the read head in hard disks

SMR

Technique that partially overlaps tracks in hard disks

Read, write

___ head is smaller than the ___ head