Difference Between HDD and SSD in Layman’s Terms
HDD and SSD
They’re both hardware devices to store data. The PC needs some way to store data even when it’s turned off, unlike its RAM which is effectively cleared when the power is disconnected. Else you’d lose all your work as soon as you turn it off or there’s a power failure – even work you did years ago. So you need either one or the other.
The effect between the 2 – SSD is faster & more expensive. Lately, they’ve become as (if not more) reliable than HDD. It used to not be the case, but these days it’s been proven to have less tendency to corruption and providing longer life-times in data retention. E.g. a HDD might start “loosing” data after 5 to 10 years (some even within 2 if they’re cheap low quality), but a high quality SSD comes with guarantees of 10 to 20 years. So the only downside these days is cost, and therefore size, as the larger (in storage terms) an SSD is the higher its price exponentially.
How it works (An analogy): Think of a library and how it would organize books to add new books and retrieve them.
HDD is like a set of isles of shelves, each having their own librarian to move up/down the isle to find a specific book. The librarians are rather restricted in their movements, they can’t easily move in more than one direction or at all. So to borrow a book you ask the head librarian and give her the book name & author (or some sort of identification like an ISBN number). She then passes along that data to the relevant sub-librarian, after figuring out which rack holds that book. The sub-librarian then figures out how high the book is (i.e. on what shelf in the isle). The shelf is moved past her until the position of the book is in front of her. She then takes it out and gives it to her superior who passes it to you.
SSD is like some futuristic library where there’s only the one librarian, and a trick which makes distances to travel a non-event. The trick makes it such that all books are in direct reach of her arms and they’re laid out in a nice grid pattern. So she can immediately pick up that book from its address and give it to you.
How it works (closer to reality):
HDD is formed like a set of discs (think of it like DVD’s stacked on top of each other). Each side of the disc is coated by a substance which can be changed slightly by placing a magnetic field over it. The discs are like the isles in the library. Each side of each disc has a head (analogous to the sub-librarians, but this librarian uses magnets to both place and retrieve the book or data) which can be swung outward or inward to the line in which the data is saved. It then waits until the disc has spun past until the relevant position is directly in front of it. Since the magnetic property can either show as north / south several positions are needed for any little bit of data, e.g. usually a single character need 8 spots coded something like Morse code. After reading each spot its N/S is sent to the controller (head librarian) who then organizes them in order to send to you.
SSD is a grid of interconnected “switches”. These can be tested or set using an electrical signal. The main controller simply sends down the correct wire to find the correct switch (or rather set of switches). It then interprets the result of those wires (which are on and which are off) into the contents similar to the spots read by the heads in the HDD.