Everything You Need to Know About SSDs

Solid-state drives (SSDs) are fast becoming the go-to storage device. But how do they store data, how long do they last, and what advanatges do they offer over hard disk drives (HDDs)?

What is NAND Flash?
Data in an SSD is stored in NAND flash chips, which are built up of many cells that hold bits, and are turned on or off through an electric charge, representing the data stored on the drive. The number of bits in each cells can vary, leading to different types of NAND flash such as single level cell (SLC), multi-level cell (MLC), and triple-level cell (TLC). Single-level cell (SLC) flash contains a single bit in each cell, and as such, has low storage capabilities. This type of flash is popular in the enterprise market due to its long lifespan and charge cycles compared to other levels. The main disadvantage is the high cost associated with storing only a single bit in each cell, meaning it’s increasingly uncommon in home computers. Multi-level cell (MLC) flash contains more than one bit per cell, as the name suggests. Because of the lower costs associated with this type of flash, MLC is commonly used for everyday consumer use. The main disadvantage of MLC flash is that it isn’t as durable as SLC. Finally, triple-level cell (TLC) flash stores three bits per cell, and is cheaper to manufacturer as a result. The downside is that cells are capable of withstanding far fewer read/write cycles, and as such, TLC flash is unsuitable for industrial use, and only used in consumer devices like phones, laptops and tablets.

What is the Lifespan of an SSD?
SSD’s, like HDDs, do not last forever. As we discussed above, the lifespan of an SSD can be determined by the type of NAND flash it uses. For example, SLC flash has a much longer lifespan than both MLC and TLC flash, but comes with a steeper price tag. Despite this, SSDs generally have a much longer lifespan than HDDs. Unlike their mechanical counterparts, SSDs contain no moving parts, so there’s zero chance of a physical fault like a head crash or spindle motor failure. Modern SSDs can withstand a lot of program/erase cycles, allowing you to write hundreds of terabytes of data before they fail.

Should I Choose an SSD over an HDD?
Ultimately, this depends on what the drive is going to be used for. If you require a large storage device and are on a budget, then an HDD might be best. Alternatively, if you don’t require instant access to your data, you could opt for an SSD with a smaller storage capacity, storing the bulk of your data on an external hard drive or in the cloud. If you’re looking for performance, then an SSD is unbeatable in this regard.

How Much do SSDs Cost?
In terms of cost per gigabyte, SSDs are pretty expensive when compared to HDDs. For example, you can pick up a 1TB HDD for around £50; an SSD with an equivalent capacity will set you back at least £100. But as NAND flash becomes cheaper to manufacture, the price of SSDs will steadily fall.

What is a PCEi SSD?
Most SSDs use a SATA III connection, which is capable of speeds of 6Gb/s. Some newer SSDs connect via the PCIe slot, which is used for things like video cards. An SSD with a PCIe connection is capable of much higher transfer speeds – up to 16Gb/s. But this speed boost doesn’t come cheap, and you can expect a premium price tag for the privilege. For most users, a standard SATA SSD will be sufficient, though.

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