Shopping for storage media can be a strange undertaking. In many cases, items with the same capacity and the same connector (with the same theoretically speed limits) can have very different prices. Demystifying this can be a process in itself, and comparing SSD features when purchasing one can be just as difficult.
We'll look at some of the things that differentiate SSDs and what to look for when upgrading your PC's main drive. Let's examine the differences between drives with the same top specs to find out what actually sets drives with the same capacity and connector/interface apart from each other.
The brain of an SSD is its controller
Controller technology can have a big impact on SSD price (and speed)
One of the biggest factors affecting the overall speed (and potentially lifespan) of an SSD is its controller. The controller is the brains of an SSD and manages many of the onboard processes that are managed by the SSD, as opposed to your operating system. When an SSD is connected to your computer, it provides a unified API, a standardized interface available for your operating system to interact with. This is used to manage your data, make changes to the disk, or request information, but it does not manage processes that are native to the SSD, such as garbage collection, wear leveling, and error correction.
Some of these features are more important than others. A quality controller will have all of the above. Effective wear leveling can significantly extend the life of your SSD. A good controller can make the difference between an SSD that stays fast and powerful for a decade or more and one that dies after a few years. Most controllers from reputable brands are high quality and support all of the features you're probably concerned about. However, this is something to seriously consider when buying a budget SSD from a lesser-known brand, as controller quality can vary widely.
Drives have their own DRAM cache
DRAM cache is critical for speed and throughput
Another factor that can affect SSD price is the quality and quantity of the DRAM cache on the SSD itself. This DRAM cache functions analogously to the L3 cache on your CPU, providing a small but fast buffer that can be used for a variety of functions, such as quickly accessing your SSD's mapping table or a temporary buffer for data writes. It keeps things easily accessible to support higher speeds. The existence of a cache can significantly affect the performance of your drive, and a larger cache can improve overall throughput (especially when multiple applications or processes are accessing data at the same time).
Some budget SSDs forgo a cache altogether, while a larger and faster cache is a key feature of more expensive enterprise SSDs. The size of a drive's cache and its technology are not often disclosed on product pages for consumer websites, but more detailed review sites like Tom's Hardware It is often investigated what cache size is available for a drive. For example: Tom's HardwareThe review of the often recommended Samsung 990 Pro contains information about the available 2 GB LPDDR4 cache as well as the integrated controller.
Some low-cost SSDs forgo a cache entirely, while a larger and faster cache is a key feature of more expensive enterprise SSDs.
More detailed specifications are often available on manufacturers' product pages, such as Samsung's product page for the 990 Pro, but these often require an experienced technical eye to understand. Adding DRAM to an SSD obviously affects its price, and again, budget SSDs without DRAM tend to have significantly lower performance, especially under high simultaneous workloads for extended periods of time.
Type of NAND flash used
The differences in NAND flash can be difficult to decipher, but have a big impact
One almost invisible difference between SSDs at different price points is the difference in quality of the NAND flash used. It can often be difficult to get information about this, but the overall quality and durability ratings of more expensive flash memory can give your drive better overall performance for longer. The endurance capacity of NAND flash memory is usually given in TBW (terabytes written). Some manufacturers may publish ratings and warranties for their flash memory, guaranteeing a certain number of writes to the flash memory before it finally gives up the ghost. However, this is not common (especially with lower-priced drives). This is another area where brand awareness and reputation comes into play, as some of the more expensive, reputable manufacturers publish data on high-quality flash memory and use it consistently. This gives these quality drives a lower failure rate and longer durability.
To use the Samsung 990 Pro as a reference example again: Samsung publishes a TBW of 600 TB over the lifetime of the drive.
There are a few other considerations when comparing NAND flash, some more relevant than others. We've covered the differences between single and multi-layer SSDs on HowToGeek. Most consumer SSDs in 2024 will use TLC (triple-level cell) NAND flash, so we wouldn't worry about this factor if you're buying from a reputable brand. Some ultra-low budget white label SSDs may use QLC (quad-level cells), which we'd avoid due to the performance penalty involved.
As with most things, you get what you pay for with an SSD
As we've highlighted before, there are some significant differences between seemingly identical SSDs that can affect performance. These are difficult to compare, especially since information on the specs of budget drives can be hard to find. We recommend sticking with reputable brands like Samsung, Crucial, and Western Digital for your main drives. If you're looking for a high-quality budget SSD, they're out there! However, be sure to research the quality of the controller used, the amount of DRAM cache available on the drive, and possibly the type of NAND flash used. All of these things can affect both performance out of the box and the longevity of the drive in the long run.
If you're looking for an easy way to compare SSDs from similar, reputable brands, comparing random read/write speeds (or IOPS) can be a good way to go – but be careful, because this often doesn't tell the whole story.