How Computers Work · Files & Storage Deep Dive · Lesson 2 of 5

Hard Drives vs SSDs

Spinning discs or flash chips: why the kind of drive changes everything.

Spinning platters and flash chips

Every computer needs a place to keep files when the power is off. That place is the storage drive, and it comes in two main kinds.

A hard disk drive (HDD) stores data on spinning metal discs called platters. A tiny arm with a read head floats just above the platter, a bit like the needle on a record player. To open a file, the platter spins to the right spot and the arm moves over it.

A solid state drive (SSD) stores data on flash memory chips, the same kind of storage your phone uses. Solid state means it has no moving parts. Nothing spins, and nothing has to move into place.

That changes speed a lot. A hard drive waits for the disc to turn and the arm to travel, thousands of times while a program loads. An SSD reaches any spot almost instantly. Most SSDs are several times faster than hard drives, and the fastest are faster still.

You can often tell them apart by shape:

• A desktop hard drive is a metal box about the size of a paperback book.
• Many SSDs are a small stick about as long as a finger, called M.2, that plugs straight into the motherboard.

To check which kind you have on Windows, search Start for Defragment and Optimize Drives. The Media type column says Hard disk drive or Solid state drive.

On the practice computer, open the same file on the hard drive and on the SSD and compare the times. Then delete a file on each one, and turn on BitLocker at the end. You'll learn what those last steps mean in the next modules.

Durability, and why SSDs felt so fast

Speed is not the only difference. Moving parts also affect how tough a drive is.

A hard drive's read head floats a hair's width above the spinning platter. A hard bump while it runs can make the head touch the platter and damage it. That is why dropping an older laptop was so risky.

An SSD has no moving parts, so it handles bumps and drops much better. It is also silent, runs cooler and uses less battery.

SSDs wear out in a different way. Each flash cell can only be written so many times. Modern SSDs spread writing across all their chips to even out the wear, and for normal home use most last many years.

Hard drives still have one big strength: price. They hold a lot of data for less money. That is why they are popular for backups and big collections of photos and videos.

When SSDs became common in laptops, people noticed a huge change. Computers that took a minute or two to start now started in seconds. Apps opened right away. The processor didn't change. The computer just stopped waiting on a slow, spinning disc.

A quick way to remember:

• HDD: spinning platters, slower, fragile when bumped, cheaper for lots of space.
• SSD: flash chips, faster, quieter, tougher, costs more for the same space.

Whichever kind you have, no drive lasts forever. Either one can fail without warning, so keep a backup of anything you would hate to lose.