How to choose a really good SSD

Recently, I realized I didn't know as much about SSDs as I thought and had been relying too heavily on CrystalDiskMark for testing. Since then, I've educated myself on SSDs, learned how to test them better, and even acquired several different SSDs for testing and experimentation.

If you're interested in learning more about SSDs and proper testing methods, please read on.

First, let's start with testing SSD speed. Many people use CrystalDiskMark for testing storage speed. However, you should know that using CrystalDiskMark is not a good way for testing speed. It's a pretty limited test that cannot emulate the real-life scenario of copying large files. Even if you select a 64 GB test file size, CrystalDiskMark will simply allocate 64 GB disk space, but will only write or read a small portion of it. This is very misleading, in my opinion.

The main issue with CrystalDiskMark is that it doesn't read or write enough data to reach the cache limits of a drive. As a result, even drives with little to no cache can display very high speeds in CrystalDiskMark. However, when you try to copy large files to these drives, the transfer speed will plummet after a few gigabytes. I've had SSDs, such as the TEAMGROUP QX 4TB, that dropped to below HDD speeds (around 50 MB/s) after copying just a few gigabytes, despite having impressive CrystalDiskMark results.

So, if you want to test the speed of copying large files, you need to do exactly that—copy large files. This might be surprising for those who rely on CrystalDiskMark. Ensure you copy from another very fast SSD so that the read performance of that other SSD will not be the bottleneck. I used my fastest internally installed NVMe SSD to copy large files from (TLC NAND memory, SLC cache, DRAM cache, up to 7 GB/s read and write speeds).

Storage drives have different types of caches. SSDs can have an SLC cache (SLC = Single-Level Cell, the fastest and most expensive type of NAND memory) and/or a DRAM cache (for example, an SSD might have a 1-4 GB DDR4 internal cache).

Consumer SSDs usually use QLC (Quad-Level Cell, which stores 4 bits per cell and is one of the slower and less reliable types of NAND memory, used in cheaper SSDs) or TLC (Triple-Level Cell, which stores 3 bits per cell and is faster and more reliable than QLC, used in more expensive SSDs). You can see how SLC and DRAM caches come into play in this example: Silicon Power XS70 Review.

More expensive SSDs also have an internal DRAM cache, which is used before the SLC cache (if an SLC cache is present). In 2024-2025, DRAM caches typically use DDR4 memory. DDR4 cache is significantly faster than TLC for sequential reads and writes and has about 1000 times lower latency than TLC (nanoseconds vs. microseconds).

The SSD controller is critically important, acting as the brain of the drive. It manages data transfer between the host computer and the NAND flash memory, directly impacting performance, reliability, and longevity.

High-quality controllers: Phison (particularly in name-brand SSDs), Western Digital’s own controllers, and Samsung’s own controllers.

Mid-range controllers: Realtek, Silicon Motion.

Lower-quality controllers: Innogrit, Maxiotek. These often suffer from firmware issues, especially in budget Chinese no-name SSDs using unmodified stock firmware, though shortcomings can persist even in some name-brand drives.

A reputable controller brand does not guarantee a high-quality SSD, however. For instance, an SSD might feature a top-tier controller but use outdated PCI-E (e.g., 3.0), have fewer channels (e.g., 4 instead of 8), lack DRAM cache, or employ slower QLC NAND memory. These limitations can significantly impact the SSD's performance, despite the controller's brand.

When choosing an SSD, if you want high sustained write speeds and reliability, look for drives with the following characteristics (often found in the SSD database here: TechPowerUp SSD Specs):

Performance-wise:

1. TLC type of NAND memory (faster than QLC)
2. SLC Cache—the larger, the better (top drives nowadays may have 1/3 of their capacity as an SLC cache). You can see how an SLC & DRAM caches come into play, for example, here: Silicon Power XS70 Review.
3. DRAM Cache—the larger, the better (ideally >= 1/1000th of the drive capacity, i.e. 4Gb DRAM cache for a 4TB SSD)

Reliability-wise:

1. Reliable controller (e.g., Phison, Samsung Pascal/Presto, WD). Research the controller of the SSD you're considering purchasing. Don't underestimate the importance of a reliable controller—almost half of my NVMe SSDs failed within the first year (Silicon Power M55, TeamGroup MP34, HP FX900) before I began choosing models with better controllers.
2. Long warranty—ideally 5 years. This is important; I recently replaced my dead 4TB TeamGroup SSD for free because it was still under warranty (although the drive failed, I have to give credit to TeamGroup for honoring their warranty).
3. High Endurance rating from the manufacturer—at least 500 times the size of the SSD. Endurance is measured in TBW (terabytes written). For instance, for a good 4 TB drive, an endurance of 4000+ TBW would be ideal, and at least 2000 TBW would be good. Keep in mind that the endurance rating does not guarantee that the drive won’t fail sooner :)

When it comes to reliability, cooling can be critical for NVMe SSDs. While some slower SSDs using PCIe 3.0 can function adequately without a heatsink, faster SSDs that utilize PCIe 4.0 or 5.0 will require effective cooling under heavy workloads, such as transferring large amounts of data to and from another high-speed SSD. In such cases, ensure you purchase an SSD with a heatsink included, or acquire a good heatsink separately and install it properly. Don't be frugal with a quality heatsink for a fast SSD that will be put under heavy load!

If you're looking for quick advice on a fast and reliable NVMe SSD, I can recommend a couple of options:

1) Kingston FURY Renegade - Best of the Best, imho:

• TLC NAND memory
• 4 GB DRAM cache
• HUGE SLC cache (1358 GB)
• Phison E18 controller
• 4000 TBW endurance rating
• 5-year warranty

(Specifications are for the 4 TB model)
I own two of these drives, and you can't beat this disk for its price.

2) Samsung 990 Pro:

• TLC NAND memory
• 4 GB DRAM cache
• 442 GB SLC cache
• Samsung Pascal controller
• 2400 TBW endurance rating
• 5-year warranty

(Specifications are for the 4 TB model)
This model may be slightly more expensive than the Kingston FURY Renegade, with a smaller SLC cache and lower endurance rating, but it is still an excellent choice for its price. You can't really go wrong with this one either.

Good luck! I hope you enjoy your future fast SSDs for many years without any issues!