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Hard disk drives (HDD) and solid-state drives (SSD) are designed for different storage scenarios, but the latter is gradually replacing traditional mechanical drives as prices continue falling. When building a new PC or looking to expand the storage capacity of an existing system, it is a good idea to learn what the differences are between SSDs and HDDs.

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SSD vs. HDD: What's the difference?

How solid-state drives and hard disk drives differ the most is in the technology used to store data.

  • HDD: Traditional method of storing data by using spinning platters and magnets. An HDD is usually far more affordable than an SSD, can endure heavier writing, and offers far higher capacities.
  • SSD: Newer technology that writes data to memory chips. An SSD requires less power, emits less noise, is considerably faster, and has no moving parts.

The hard disk drive has been around since the start of desktop computers. Even to this day, they're still used for high-capacity demands such as data centers, servers, and even gaming PCs. They're simply unmatched by solid-state drives in terms of price per GB, which is how much you can expect to spend per GB on a drive.

A 1TB HDD may cost just $30 while you'd easily shell out $60 for an equivalent SSD. That's double the price per GB of data and makes the HDD a far better value, but the SSD has no moving parts, is considerably faster, and should last longer so long as you don't hit it with heavy writing. The reasons behind this is down to the technology used to store data.

A hard drive will use a motor to spin one or more platters with a magnetic coating inside a sealed chamber. Then a moving read/write header glides across each platter to access data. The direction of the magnetization determines what type of bit is present. The best SSD is a little more straightforward as it simply uses power to access data on memory chips (or flash memory), much like a USB drive or storage inside your smartphone.

For laptops, things become interesting with choosing an HDD or SSD. Overall, SSDs are the far superior option for notebooks due to the lack of any moving parts, the increase in speed, and power reduction, the latter of which should aid with extending battery life. For desktop PCs, we'd recommend using an SSD for storing the OS and frequently accessed apps and games. HDDs can then be introduced for storing all other data.

Price

Western Digital 1TB WD Green Internal SSD and 1TB WD Green SN350 NVMe Internal SSD on blurred background
Source: Western Digital 

The price is usually what sways people away from investing in larger-capacity SSDs because they can get really expensive. This is also reflected in the price per GB. That's a metric we use to determine how much you'll be paying for each GB in a drive, which helps determine whether it's a good deal. An SSD typically costs more per GB than an HDD of equal size.

An 8TB Seagate FireCuda HDD costs $135 at the time of writing, which is considerably less than the $495 Samsung charges for its 2.5-inch 870 QVO 8 TB SSD. The HDD works out to be $0.02 per GB and the SSD $0.06 per GB. You could buy three 8TB HDDs for a total capacity of 24TB compared to just one 8TB SSD. This perfectly illustrates the difference in pricing between the two technologies.

You'll be paying more for an SSD in general, but you will gain better transfer rates and the potential for the drive to last far longer. Both a 2.5/3.5-inch HDD and a 2.5-inch SSD will all use the same SATA interface. M.2 SSDs require M.2 slots found on motherboards inside desktop and laptop PCs. Please check what ports are available before buying new drives.

Performance

When it comes to measuring the performance of a drive, we have a few metrics to work with. Sequential read/write largely covers moving huge files. A typical hard disk drive can reach up to 150MB/s before topping out. A 2.5-inch SSD can achieve up to 500MB/s, but you can go all the way up to 8,000MB/s with the fastest NVMe PCIe SSDs. An SDD will allow you to read and write data at considerably higher speeds.

Crucial MX500 CrystalDiskMark
Speeds were recorded using the Crucial MX500 2.5-inch SATA SSD.
Source: XDA-Developers

This is useful for builds where games and other heavy software are stored on the SSD. It's also important for those who work with larger files like 4K or 8K video. Hard drives are excellent at storing lots of data on cheaper platforms, but the technology doesn't come close to what's possible with flash memory modules on SSDs.

Endurance

Endurance is a tricky one when looking at SSD vs. HDD since both drives are better in their own way. Let's start with the HDD. Because of its mechanical nature, it's clear this would be the first device to fail over long periods. The motor has to spin the platters and the head has to move back and forth over each disk, which can lead to wear when hit hard with access requests.

But hard drives aren't susceptible to heavy write decay like an SSD. You can safely write as much data as the HDD can handle reading without causing unnecessary wear. The same cannot be said for an SSD, which again is down to the technology and how data is stored on the flash memory modules. SSDs usually have a finite amount of data that can be written onto the drive before you start to encounter issues.

It's worth noting that this figure is usually a seriously high amount of data. The 1TB Samsung EVO Plus NVMe SSD has a terabyte written (TBW) endurance rating of 1,200TB. That means you can write 1,200TB (or 1,200 times the capacity of the drive itself) before you start to see a degraded performance or some other issue with the drive. Other than this, an SSD has far better endurance due to the lack of moving parts.

Should you buy an HDD or SSD for your PC?

We'd always recommend a hybrid approach to storage inside a PC unless it's a laptop, or you have enough cash to cover the cost of an all-SSD configuration. SSDs simply make more sense inside a notebook PC thanks to the lack of any moving parts and better battery life compared to an HDD. For a desktop, it's best to use an SSD for the operating system and frequently used apps and games, as well as an HDD or two for other data.

Using an SSD in your PC can save you some money whilst providing a modest boost in performance, which makes it ideal for games and software that you don't always play or use, but would work better with the increased bandwidth over HDDs. An M.2 SSD drive can be vastly more capable with faster transfer speeds, but you'll be paying a small fortune for the luxury and need to ensure you have an open M.2 port on your motherboard.

The Samsung 970 Evo Plus SSD.
Samsung 970 EVO Plus SSD

An M,2 NVMe SSD such as the Samsung 970 EVO Plus would be excellent for storing the OS and all your favorite apps and games. It requires a PCIe M.2 slot, which is a common sight on most modern motherboards.

WD Blue SA510
Western Digital Blue SSD

2.5-inch SSDs are considerably more affordable than PCIe NVMe drives, but they don't offer such ridiculous transfer speeds. The Western Digital Blue SSD family hits speeds of up to 555MB/s, but they're still much faster than HDDs and have no moving parts.

seagate-barracuda
Seagate BarraCuda Compute HDD

The Seagate BarraCuda Compute HDD is a 3.5-inch drive that is perfect for users who want to have the most cost-effective price per GB hard drive with storage options from 1TB to 8TB of space,