What’s an SSD? Here’s everything you need to know (with video)

For a long time, the only way to store information on your PC in a long term, easily accessible manner, was to use a hard drive disk, which is a technology that dates all the way back to the 1950s. The refrigerator-sized IBM 305 computers shown below held 3.75 megabytes of data each, which is just about the amount of data used to store one photo taken by a modern mobile phone.


Inside, hard drives feature a moving arm that writes data onto a spinning disk. Out of all of the types of memory in a modern computer, hard drives are still the most cost effective way to store lots of data, but they’re also the slowest.

By comparison, solid state drives (SSDs) use flash memory, which involves no moving parts. Flash memory is much faster than disk-based memory, but it comes with a higher cost.

Thankfully, flash memory technology evolves quickly. Prices continue to drop while storage sizes are on the rise, making SSDs an increasingly viable alternative to hard drives for PC users.

Improvements over traditional hard drives

This logarithmic graph shows a rough speed and size comparison between SSDs, hard drives, and RAM:


SSDs clearly fall in the middle between RAM and HDDs when it comes to speed and size. They’re about 10x faster than hard drives, while still being more than 10x slower than RAM. But they have the benefit of working as a long term storage option, just like a hard drive, even if they can’t currently store as much data, and they can’t do it as cost-effectively.

Let’s take a look at a couple SSDs and an HDD taken from some of our office computers:


First, the Samsung 850 EVO SSD. Ours has 120 gigabytes of storage, and it transfers data at around 500 megabytes per second. It uses a SATA connection, the current standard connection for a hard drive, which maxes out at about 600 megabytes per second.


Next, a Western Digital Blue HDD. Ours has 1 TB of storage, and it transfers data at around 130 megabytes per second, making it about 4x slower than the Samsung SSD. It’s also bigger and heavier. It also uses SATA connections.


Finally, a Samsung SM951 SSD. It looks different than the first SSD because it connects to the M.2 PCIe port directly on your motherboard, instead of using SATA, allowing for even faster transfer speeds than SATA. Our SM951 has 256 gigabytes of storage, with transfer speeds of around 1,500 megabytes per second, triple the speed of our other SSD and more than 10x the speed of our hard drive.

Let’s compare the performance of these three storage devices:


On the left we have our fast PCIe SSD, in the middle is our standard SATA SSD, and on the right is our HDD. Sequential speed is measured in blue, and represents how fast large files like videos will transfer. 4K Input Outputs per second is measured in green, and represents how quickly small files are accessed and transferred. In this category, the SSDs are so much faster that the results from the hard drive aren’t even visible on the graph.

Real-world benefits

So, huge numbers on a graph are fun, but what are the real-world benefits of having an SSD?

For starters, an SSD will load everything on your PC faster than a hard drive. For example, if you install your operating system on an SSD, your PC will boot up significantly faster.


In this PC World benchmark, booting Windows on the same computer took 63 seconds with a classic 7200 RPM hard drive, and only 23 seconds with an SSD, making the SSD boot almost 3x faster. Other tests have shown that SSDs can boot at least 6x faster than hard drives.

SSDs will also load any application on your computer significantly faster, and generally make the PC’s overall performance feel snappier — especially if you install an SSD in an older system.

Upgrading to an SSD doesn’t just mean you’ll have a faster storage device. It means everything on your computer will load faster. Going from a system with just a hard drive to one that includes an SSD is probably the single most noticeable upgrade you can perform. I like to compare it to switching from dial-up internet to broadband.

To benefit from the speed of SSDs while not having to sacrifice storage space, many people include both an SSD and a hard drive disk in their PC. They’ll install their operating system and their most commonly used applications and games on the SSD, and then use the hard drive more for storage of their files, such as videos, images and documents.

For example, we just took these two drives out of one of our office computers. We use our SSD for operating Windows and some of our most-used applications, and then we use this 1 TB hard drive for all of our files. The PC feels amazingly fast, even though we went with relatively cheap storage options for both the SSD and the HDD.

SSD types

So, how do SSDs work and what types of SSDs are out there?

We’ve already talked about older slower SATA and newer faster M2 PCIe SSDs. Different SSDs also use different types of flash memory. The original SSD type is called SLC, and stores one bit of data per memory cell. SLC is still used in some enterprise SSDs where maximum reliability is valued over cost.

MLC and TLC are newer types that store more data in the same amount of space, sacrificing a bit of reliability for cheaper cost and more storage capacity. 3D, or V-NAND, is a further enhancement to fit more data in less space, and involves stacking a bunch of memory cells on top of each other.

Flash die from SSD

Here we can see inside a Samsung 850 Pro SSD. The black packages on the green board contain the Flash memory chip, which are expanded above. Each flash memory chip contains billions of memory cells. You can see a 3D stack of a few thousand if we zoom in on a small section.

Reliability and endurance

If sacrifices in reliability are made to fit more data in the same amount of space, how reliable are SSDs? Should you be worried about storing your important data in this little magic boxes?

The short answer is that SSDs are at least as reliable as hard drives in a desktop, and are a way better choice for a laptop, because they don’t have any moving parts to break if they get dropped.

Endurance was a problem with early SSDs because the individual memory cells of flash memory wear out faster than the magnetic disk of a hard drive. With modern SSDs, this is no longer an issue for normal users. Even a low endurance modern SSD could withstand writing 100 GB of data every single day for 20 years. That’s a lot. A fairly heavy computer user may write about 5GB of data per day. So we don’t have to start worrying about the endurance of our SSD for at least 380 years.

Other factors affecting the reliability of an SSD are very similar to the rest of the parts in your computer. SSDs contain solid state capacitors, firmware, a PCB, electrical connectors, and all of the other little parts that can, and do, occasionally fail. So, modern SSDs are quite reliable, but will still occasionally fail. Whether your data is on an SSD or a hard drive, always back-up anything important!

A couple additional advantages of SSDs are power use and noise. SSDs are silent, because they have no moving parts. If you’re a fan of quiet computers, this gives SSDs another big advantage over hard drives, which can often be heard reading or writing with their spinning disk and moving parts.

SSDs also use less power. This is more helpful for laptop battery life, and doesn’t matter as much in a desktop because the amount of power that either SSDs or HDDs use is so small compared to the power use of the CPU, graphics card, and monitor.

SSDs: Logical Increments approved

Close-up: In conclusion: If you can afford it, we highly recommend getting an SSD. You should at least consider adding a small SSD to install your operating system on, as it’s one of the most noticeable PC upgrades you can make.

Generally speaking, all modern SSDs are fast and high quality. Your personal choice will mainly come down to size and price, unless you want to look at a bunch of benchmarks to figure out which will get you that extra little bit of performance.

When shopping around for an SSD, we recommend looking at reviews and recommendations from reliable sources to make sure you’re making a well-informed choice. We’ll provide a few helpful links in the video description below.

Thanks for reading. If you have any questions, leave them in the comments. And if you’d like to learn more about PC hardware, see our full list of PC build recommendations at logicalincrements.com.