Buying a new device is never easy the first time around, especially if it requires you to know all kinds of jargon to even have an idea of what you’re purchasing. As awesome as they are, solid-state drives suffer from this issue.
Fortunately, while SSD specifications may seem overly daunting at first, the truth is that these terms are quite simple to understand. So if the only reason you haven’t bought an SSD yet is due to confusing jargon, please reconsider!
So, here are seven important terms that you should know before buying an SSD.
1. Form Factor
The form factor of an SSD describes its real physical size according to a particular standard. As a term, it’s used for more than just SSDs (e.g., motherboards and HDDs), but the idea is the same throughout: how big is this particular thing?
Form factor is important because it determines whether or not the SSD will fit inside your computer.
For SSDs, most options come with a form factor of 2.5-inches, which coincides with laptop-sized HDDs. Compare this to desktop-sized HDDs, which have a form factor of 3.5-inches. SSDs don’t naturally come in this size, but you can encase them in a 2.5-to-3.5″ adapter.
One related consideration is the z-height, which describes how tall the SSD is when laid flat. For example, two SSDs that are both 2.5-inches could have different z-heights—meaning one might be too thick for your computer while the other just fits.
However, 2.5″ isn’t the only SSD form factor. SSDs also come as modules, typically known as M.2 NVMes and M.2 SATAs, mSATA, SlimSATA, and more.
2. IOPS
When it comes to SSD performance, one important specification that you should check is IOPS (pronounced “eye-ops”), which stands for Input/Output Operations Per Second.
In layman’s terms, IOPS estimates how quickly the SSD can read and write random packets of data across random sections of the drive. This simulates the average user’s real-world conditions of normal, everyday usage. Higher IOPS is always better.
IOPS should not be confused with sequential read/writes, which is a different measurement of how quickly the drive can read and write big chunks of data to a specific drive location. This simulates the transferring of big files. Higher is better in this case, too.
3. Write Cycles
The architecture of an SSD comprises many different cells grouped into pages and many different pages grouped into blocks. Unfortunately, these blocks cannot be selectively overwritten—instead, the entire block has to be erased before new data can be written to it.
Every time a block is erased and written to, it’s called a write cycle. Why is this important to know? Because blocks have a finite number of write cycles before reaching a point where they can’t write new data anymore.
Fortunately, SSD manufacturers have mitigated some of this by implementing wear leveling. Different SSDs implement different kinds of wear leveling, but the end goal is all the same: waste as few write cycles as possible to prolong SSD lifespan as much as possible.
Here’s the good news: at this point, SSDs are advanced enough that write cycles don’t matter anymore for the average user. So it’s really only a concern for data centers and enterprise businesses that write gigabytes of data every single day.
4. TRIM
SSDs with TRIM support became big news several years ago, but if you’re still confused about what TRIM support actually is—or if you’ve never even heard of it until now—then rest assured that you aren’t alone.
TRIM (which isn’t actually an acronym) is a method used by SSDs to prevent performance degradation over time. To understand why this works, let’s revisit how SSDs store data.
Remember that SSD memory blocks must be erased before new data can be written. What if a block is half-full, and you just want to fill up the other half? You have to store the first half of data somewhere else, erase the block, then rewrite the first half of data plus whatever new data you want to add.
TRIM allows SSDs to delete specific portions of data within a block. That way, when new data needs to be written, the drive doesn’t need to go through the whole process of backup-delete-rewrite. It can just write.
5. MTBF
MTBF stands for Mean Time Between Failures. It’s a statistical measurement that predicts the rate of failure for a particular SSD model given a population of 1,000 SSDs of said model running 8 hours per day.
So when you hear that the Samsung 850 EVO 250 GB has an MTBF of 1.5 million hours, it means that in a population of 1,000 of this particular SSD running 8 hours a day, one of those drives will fail every 187.5 days:
1.5 million hours / 1,000 drives / 8 hours per day = 187.5
Most people interpret MTBF as “this drive will, on average, last me 1.5 million hours”, which is completely wrong! In fact, 1.5 million hours translates into 171 years. That would be absurd!
6. Controller
Although SSDs are not used for any computer processing (that’s what CPUs, GPUs, and ALUs are for), they do have something called a controller, which is like a built-in processor that manages a lot of the SSD’s features: reading, writing, wear leveling, garbage collection, etc.
An SSD’s controller is one of the bigger differentiating factors between brands and models. However, in the grand scheme of things, the average user won’t be able to tell between controllers, so it’s not something you should worry too much about.
When choosing an SSD to buy, focus more on the specifications and reviews than on the controller itself.
7. SLC, MLC, or TLC
The actual memory cells in an SSD can be one of three types: single-level cell, multi-level cell, or triple-level cell. These describe how many bits can be stored per cell (1, 2, or 3, respectively). For consumer-grade drives, SLC and MLC are the more common variants.
Here’s what it all means for you: SLC drives are more stable but more expensive, while MLC drives are more cost-efficient to produce but more prone to data errors. In general, MLC also tends to be slower than SLC. TLC, which is newer than both SLC and MLC, is the most cost-efficient but even more prone to errors.
Not sure which one to choose? For capacity, consider a TLC drive. You’ll get the most storage per dollar, but it may die on you. For reliability, go for an SLC drive. This is ideal if you really can’t risk drive failure. If you want a bit of both, swing for an MLC drive.
SSDs Truly Are Worth It
Hopefully, we’ve addressed any reservations you might have about shopping for an SSD of your own. At the end of the day, we believe that SSDs beat out HDDs in nearly all cases. So only get an HDD if your budget is extremely tight or you’re using it as a bulk storage drive.
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