SSD and HDD: What’s the difference?

For the past few years, solid-state drives (SSDs) have become quite popular in the computing world, mostly because of how fast they are compared to hard disk drives (HDDs). So, what exactly sets an SSD apart from an HDD?

Nowadays, computers use non-volatile medium for storage, which means data that’s stored in it doesn’t get lost once the computer shuts down. Storage for modern-day computers and notebooks have been handled by hard disk drives for the longest time and it’s only now, with SSDs becoming more affordable, that consumers are seeing a different storage medium in their computers.

Hard disk drives have mechanical parts

If you aren’t familiar, hard disk drives store data on circular disks made up of aluminum, glass, or ceramic that are coated with a magnetic layer, often called platters. Since these platters are responsible for holding the data, the storage capacity of an HDD is dependent on how many platters it has.

The big disks are the platters and the arm hovering above is the actuator arm.

When the computer’s processor sends out instructions to read and write data, the motor on the drive moves the actuator arm across the platter. At the end of the actuator arm are the read/write heads which are made up of tiny magnets responsible for reading data already stored on the platter or writing new data on the empty spaces on the platter. The combined movement of the actuator arm and the rotation of the platter allows the computer to read and write data, which is kind of like the arm of a record player touching a vinyl record to play music.

Having all these moving parts means an HDD’s read and write speed is dependent on how fast the platters can rotate and how fast the actuator arm can track locations on the platter. These parts can only move up to a certain speed or else they’ll break down, and nobody wants a broken storage device. As with all mechanical parts, heat and noise are by-products of their movements, which is why an HDD can become hot and/or noisy during operation.

Solid-state drives have no moving parts

From its name, an SSD is a drive that uses a type of solid-state storage called flash memory, which is also a non-volatile storage medium, to store and retrieve data. Each flash memory chip found in the circuit board of an SSD contains memory cells that are made up of floating-gate transistors, which are a special type of transistor that can store or discharge an electrical charge in its cage-like part called the floating gate. The storing capability of these transistors is what allows the data to remain, even when there’s no electricity flowing through them.

Inside an SSD is a circuit board with a bunch of embedded chips, including the flash memory, controller, and cache.

As mentioned, an SSD doesn’t have moving parts like the actuator arm and motors of an HDD. Instead, it has an embedded processor called a controller. Much like the computer’s processor, the controller does all the heavy lifting, as it’s the one responsible for locating the blocks of memory where data can be read or written to.

This is also the reason why SSDs perform faster than HDDs; since they don’t need to wait for any moving parts to read or write data, the controller just needs to receive the instructions from the computer’s processor and it can start reading or writing data.

SSDs may not suffer from a mechanical breakdown, but they’re far from faultless. Flash memory can only have data written and erased a finite number of times before its cells degrade and become unreliable. This means an SSD can only write a certain amount of data before it fails, which is why SSD specification sheets typically include Terabytes Written (TBW), so consumers know how much data can be written into the drive before it eventually fails. However, SSDs these days can last more than ten years in typical day-to-day usage.

Both storage mediums have pros and cons

So, is a solid-state drive better than a hard disk drive, or vice-versa? Sadly, there’s no simple answer to this question, as it all depends on the needs of the consumer, which usually involves speed and storage capacity.

On one hand, if a person wants faster read/write times, an SSD is the clear winner, but you’ll lose out on storage capacity, since most SSDs today start from 120GB and can only go up to 1TB or 2TB. Mind you, those high-capacity SSDs will surely burn a big hole in your wallet.

On the other hand, if a person values capacity more, an HDD is the better option, with drives typically ranging from 500GB to 6TB of storage capacity for mainstream HDDs. Also, HDDs don’t cost an arm and a leg compared to SSDs if you want to get large-capacity ones.

With these in mind, there’s no stopping consumers from having both an SSD and an HDD in the same system. Setting up an SSD as your main drive with the operating system and other important software, while having a secondary HDD to store all your media and personal files, would net you the best of both worlds: a speedy system boot up without sacrificing storage space.

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