What is an SSD?

Solid-state drives are an invention that revolutionized computing. These hard drives use flash memory chips to deliver faster speed. SSDs have longer lifespans and lower failure rates.

It’s easy to feel confused if you’re shopping for a new computer or want to replace your old hard drive. Our SSD guide will give you a better idea of how these drives work, what their advantages are, and what the differences between different types of SSDs are.

What is a solid-state drive?

Close up of the WD Blue 3D NAND SATA SSD connector pins

Solid-state drives work differently than a traditional hard drive (HDD). Where HDDs use spinning disk platters to access information, SSDs store data on flash memory chips, much like a smartphone, USB drive, or slimline tablet. All of those memory chips are accessible at the same time, making it much easier to access that information at high speed since the drive doesn’t have to wait for any kind of platter to spin to the right point to find the information.

It’s that lack of moving parts which makes it solid state.

SSDs are built differently because of this and are available in a variety of different shapes and sizes. They are more expensive to manufacture though, and even as prices come down, in 2020 they remain more than double the cost of hard drives at a similar capacity. Especially for the fastest and largest SSDs.

SSD advantages

Samsung T5 SSD review
External SSDs are becoming more popular too.

Solid-state drives are becoming far more common in everything from high-end gaming PCs to entry-level laptops, and with good reason. They have a number of advantages over traditional hard drive storage, and embedded flash memory (eMMC).

No moving parts: The big problem with moving parts in hard drives is that they are a major point of failure. That is, if any of the moving parts break, the entire drive becomes unusable. That makes hard drives vulnerable to drop damage and wear over time. Solid-state drives have their own lifespan limitations, but they’re generally more durable and reliable because there are no moving parts to damage and no drive motor to break. That makes SSDs great for portable, external drives which may be subject to more rigorous use and handling.

Speed: SSDs can write or read data at incredible speeds compared to HDDs and even eMMCs. They enjoy far greater sustained read and write speeds — useful for transferring large blocks of data. But more crucially, their random access times are in microseconds, rather than milliseconds. That’s why SSD systems boot up so fast, games load so quickly, and systems based on SSD technology just feel snappy and responsive.

Mobility: SSDs are smaller and lighter than previous drives. This makes it possible to create today’s ultra-thin laptops, tablets, and other mobile devices. The thinnest SSDs are just millimeters wide and only a few inches long, making them ideal for the smallest of high-speed devices.

Low failure rates: After years of development, SSDs malfunction far less often than HDDs and they maintain their speed throughout their lifetime too. This is down to widespread material improvements and features like ECC, or error-correcting code, that keep SSDs on the right path.

Size and Design: SSDs can come in many different shapes and sizes, depending on how many chips they have and how those chips are arranged. They can fit into a graphics card slot, 2.5-inch drive bays, and M.2 slots. There’s an SSD for almost any occasion and that makes them far more versatile than other types of storage.

Longer lifespan: Every SSD has a lifespan that’s limited by wear on the drive’s ability to properly store the electrical charges sent to it. Lifespan tends to be measured in the numbers of terabytes that can be written to the drive before the flash cells degrade. That can equate to a decade or more of use for a typical buyer. Research has shown that not only do SSDs last longer than HDD counterparts, but they also last longer than experts expected.

Types of SSD

SSDs come in a few different shapes and sizes and that can affect their speed, their storage capacities, and even their thermal output.

SATA III: SATA III is the last evolution of an older connection option that works with both HDD and SSD. It was very useful during the transition from HDD to SSD, as hard drive compatible motherboards could then work with the new standard. It’s still the most common one used in modern SSDs, but is by far the slowest, at around 550MBps. It also involves a SATA cable connecting the drive to the motherboard, so it adds clutter.

PCIe: The Peripheral Component Interconnect Express or PCI Express (PCIe) slot is more typically used for graphics cards and add-in cards like USB ports and sound cards. But there are now PCIe SSDs that can use all the additional bandwidth for exceedingly fast data transfers. The latest-generation, PCIe 4.0 drives first launched on AMD’s X570 motherboards, can deliver sequential read speeds up to 5,000MBps, and write at up to 4,400MBps. Their prices are often more than double that of their SATA counterparts, and all that extra bandwidth doesn’t always equate to a big difference in real-world usage.

M.2: The smallest of the SSD designs, M.2 drives can leverage SATA or NVMe controllers (which can be a little confusing) so speeds do vary, between two extremes, but in terms of physical size, M.2 drives are minuscule. They have a short pin connector and typically lie flat against a motherboard, making them extremely low profile. Their compact nature can make them quite hot though, especially for the fastest drives, so they often feature heatsinks or heat spreaders like RAM.

NVMe: Non-Volatile Memory Express, or NVMe, is the underlying interface that allows almost all PCI Express and M.2 SSDs to transfer data to and from the host system. When combined with either of those physical interfaces, it allows for the fastest speeds and is what you want if you are looking for the most capable of storage.

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