10 Important Terms Every SSD Buyer Should Know

Solid-state drives have become the pillar of modern computing and data storage. It has successfully replaced the traditional hard drives in a range of devices from gaming PCs to ultrabooks and big data servers. The ultimate speed and extremely low power consumption have made it one of the most preferred choices for users who are looking for a durable option alongside boosted performance. 

However, picking up the right SSD is not as straightforward as you think. If you have ever approached a shop to buy an SSD, you must have encountered many unfamiliar terms such as NVMe, NAND, TBW, etc. While it’s not always necessary to understand everything about an SSD, it’s always a wise idea to make yourself familiar with some of them that can make a difference between buying a simple SSD that works and one that offers durability, speed, and the best value for money. 

In this article, we will look at the essential SSD terms that every buyer should know. In the end, you will be well-informed about what you are purchasing matches both your budget and the performance expected.

1. NAND Flash

One of the most important terms that you should be aware of is NAND Flash. NAND Flash is where the actual data will be stored. It’s a non-volatile type of memory that retains the data even when the power is cut off. NAND-based SSDs have no moving parts and are faster, quieter, and more durable. Now, in a single NAND flash memory cell, one or more bits of data can be stored in the form of 0s and 1s. The more the number of bits in a single cell, the higher be chances of errors and data loss.

It is important to check the NAND flash of an SSD because it determines your drive’s endurance and performance. For consumer drives, we get only two options, i.e., TLC and QLC NAND. TLC is better than QLC in every way except the price. QLC drives are cheap but less reliable. SLC and MLC NAND flash can be found only in enterprise SSDs. Now, in NAND flash, there are other things to look for, like layers, topology (charge trap or floating gate), raw speed, program time, erase time, etc.

If you don’t want to get too much into the details, just try to go for the TLC NAND flash if you can afford it. QLC offers higher capacity for the same price, but, as we discussed, is less reliable.

2. NVMe (Non-Volatile Memory Express)

NVMe stands for Non-Volatile Memory Express. It is a protocol for SSDs to communicate with the system via the PCIe (Peripheral Component Interconnect Express) interface. Unlike older SATA, NVMe offers a faster data transfer rate with significantly lower latency. 

Practically, NVMe is made to deliver read/write speeds 7x faster than SATA SSDs. Modern computer motherboards support NVMe, although it’s always advisable to check if the system has an M.2 slot with PCIe lanes or not before buying an NVMe SSD. 

The performance of NVMe depends on the PCIe generation. 

• Gen 3: Up to 3,500 MB/s
• Gen 4: Up to 7,000 MB/s
• Gen 5: Over 12,000 MB/s (emerging tech)

3. SATA (Serial ATA)

SATA stands for Serial ATA interface. SATA, although faster than traditional SSDs, is slower than NVMe, as talked about earlier. The latest and prevalent version of SATA is SATA-III, which has a maximum transfer speed of 600 MB/s with a maximum bandwidth of 6 GB/s. 

In the real world, not much difference can be noticed. SATA still feels fast for everyday tasks such as launching apps, browsing, and booting up, but NVMe always has an edge over it as it drastically reduces the load times in large file transfers. In modern and faster computers, SATA SSDs can cause bottlenecks, but there is always room for a SATA drive for backups and raw file storage.

SATA drives come in two form factors, which are M.2 SATA and SATA 2.5″ SSDs. There is no difference in the performance but the form factors are different of the both.

4. Read/Write Speeds

It’s another important term that you should not miss out on knowing about. There are two types of speed in any drive for reading and writing. The sequential read/write is always faster than the random one, as the blocks of data are stored and fetched sequentially. Advertisements can boast higher read/write speed than what you get when purchasing, It is always a wise decision not to rely on the read/write speed as the actual performance may vary based on different measures such as drive heating, lower queue depth, hardware limitations, etc. Read/write speed is a term you should be aware of about SSD, not because it will decide what you will pick up, but because it will decide what you won’t.

Higher random read/write performance is what matters the most in real-world applications like running software or loading operating systems. Sequential read/write speed is more about the big files.

5. TBW (Terabytes Written)

TBW stands for Terabytes written, and it is the measure of how much data you can write to the SSD before it starts to degrade. It directly indicates the endurance or lifespan of the SSD. Not necessarily that the SSD stops working after hitting the TBW, but it’s the cap claimed by manufacturers after which they are not responsible for the data integrity. An average user writes about 20-50 GB data per day. Even if we take 50GB per day, a 300 TBW drive would last over 16 years. So it’s always advisable to check the TBW of the drive. 

6. DRAM vs DRAM-less SSDs

DRAM is a caching technology that is used in most SSDs to store a mapping table of the data to locate it quickly. This significantly increases the read/write speed, especially in the case of random tasks. Although DRAM-less SSDs are cheaper, SSDs with DRAM are faster and more reliable for heavy tasks. Some SSDs mimic DRAM with the help of HMB (Host memory buffer), which in actuality is a small part of your system’s RAM, but they are not still not as fast. So, SSDs with dedicated DRAM are always a better choice. 

7. Endurance and DWPD (Drive Writes Per Day)

Endurance or DWPD is a very similar thing to TBW — both are the measure of the amount of data written into the drive over its lifetime. However, there is one small difference in these two metrics – TBW indicates the total amount of data that can be written to a disk before its failure, while DWPD indicates how much full drive writing can be performed daily, provided the warranty period. DWPD metric is more important to the consumer, who tends to write data constantly, such as enterprises and servers, while TBW metrics are good for consumer SSDs.

8. Controller

The SSD controller can be referred to as the main functioning component of the SSD. It is responsible for the storage, access, and management of data on the NAND Flash. It plays a crucial role in managing tasks like wear leveling and error correction, ensuring data integrity. An SSD with a good controller also has fast and stable performance during sustained workloads as well as short tasks. Popular controller brands are Samsung, Silicon Motion, and Phison.

9. Form Factor

If you are buying an SSD, you must be aware of the form factor. It refers to the physical shape, size, and connector that it comes with. The following are the most common form factors. 

2.5-inch SATA – It resembles a small hard drive, connects via SATA cable, and can fit in most laptops or desktops. 

M.2 – It is a slim, stick-like design that fits directly into the motherboard slot provided. M.2 either uses SATA or NVMe interfaces for connections. 

mSATA – It is a mini version of SATA  that can be used in compact devices. It is found mostly in the older drives and is rare to see in modern systems.

The right form factor depends on the slots of your device and the performance you need. M.2 NVMe SSDs are the most popular today. 

10. MTBF (Mean Time Between Failures)

MTFB stands for Mean Time Between Failures. It estimates how long the SSD is expected to operate before a failure starts to occur. It is measured in hours. High MTBF marks better reliable SSDs. For example, a drive with 1 million hours MTBF  could last over 100 years on paper. If you are a consumer, MTBF might seem a less practical measure than other metrics like TBW or the warranty period, but it gives you a clear picture of how long an SSD can last in real-world uses.

Conclusion

For an informed purchase, it is always important to understand terms related to the product. Understanding key terms like NAND, NVMe, SATA, SLC Cache, etc, empowers you to make a better decision in purchasing an SSD. 

If you are a particular type of user, you can consider these use cases:

• For Gaming: Give priority to NVMe M.2 SSDs with DRAM and good TBW. 
• For Productivity: Give priority to endurance, dedicated DRAM, and PCIe Gen 4 support. 
• For Servers: Give priority to SSDs with high DWPD, SLC, or MLC NAND with the support of a strong controller.