How We Test SSDs

Upgrading your desktop or laptop to a solid-storage solution—whether that's a traditional 2.5-inch drive or a cutting-edge M.2 one—is a quick, often inexpensive way of adding some much-needed performance to an aging system. By installing a solid-state drive (SSD) in your desktop or laptop, you can drastically reduce the amount of time files, applications, and even operating systems take to load, install, or copy versus older platter-based hard drives. As long as you have the slots, ports, or bays necessary, the amount of movies, photos, and games you can shuttle onto or off of one machine is almost limitless.

To make sure you always get the best bang for your storage buck, we here at PC Labs have developed an exhaustive testing suite. A mix of industry-standard tests, "trace-based" measures (more on what that means in a moment), and home-cooked trials, it runs each drive we review through a series of real-world and synthetic scenarios to help us determine which drives are the fastest, which are the slowest, and who falls in between.

Mind you, with SSDs, speed isn't everything. We also evaluate drives on the basis of value for money and additional features, such as warranty, durability ratings, and supplementary software. But SSDs have become so good these days that sometimes it's subtle things that separate an average drive from a winner.

The Testbeds: The Systems We Rely On

Depending on the bus architecture (PCI Express vs. SATA) and connection protocol (M.2 or 2.5-inch for internal SSDs; USB or Thunderbolt for external SSDs), we test any drive that comes through the labs on a certain single testbed, or pair of testbeds, among three testbed systems.

PCIe 3.0-Based M.2 Internal SSDs; Serial ATA 2.5-Inch or M.2 Drives

These drives are tested on our main Windows 10-based storage testbed. This is a resolutely high-end PC. It is equipped with an Asus Prime X299 Deluxe motherboard with an Intel Core i9-10980XE processor clocked for a max boost frequency of 4.6GHz. We use 16GB of DDR4 Corsair Dominator RAM clocked to 3,600MHz, and the system is using an Nvidia GeForce RTX 2080 Ti Founders Edition as its discrete graphics card to power video. This PC represents a state-of-the-art high-end desktop configuration, with an SSD boot drive as the primary drive and the drive being tested configured as supplemental storage.

M.2 drives on this system are installed in a secondary M.2 slot below the video card and configured as secondary storage. (The X299 motherboard we use supports both PCI Express M.2 and SATA M.2 drives.) Traditional 2.5-inch SSDs are installed on the first SATA port powered by the motherboard's main SATA controller, and installed in a 2.5-inch bay.

PCIe 4.0-Based Internal SSDs

PCI Express 4.0 M.2 SSDs are an emerging class of M.2 SSDs that offer higher potential sequential-throughput speeds than PCI Express 3.0 ones. At this writing, PCI Express 4.0 support was available only on AMD-based systems using the X570 and B550 chipsets for Ryzen CPUs, and the TRX40 chipset for Ryzen Threadripper chips. All are M.2 drives. You can use a PCI Express 4.0 SSD in a 3.0-only motherboard, but it will bounce down to 3.0 speeds.

As a result, to test the speed potential of these drives, we needed a different testbed from our main one. This specialized testbed uses an MSI Godlike X570 motherboard with an AMD Ryzen 9 3950X CPU installed. We use the same 16GB of DDR4 Corsair Dominator RAM clocked to 3,600MHz, and the system employs the same Nvidia GeForce RTX 2080 Ti Founders Edition as its discrete graphics card.

External SSDs

We use two testbeds here. The first is the same system as our PCI Express 3.0 testbed (Asus Prime X299 Deluxe motherboard, Intel Core i9-10980XE processor, 16GB of DDR4 Corsair RAM, Nvidia GeForce RTX 2080 Ti Founders Edition discrete graphics card). Drives are tested attached to this motherboard's sole USB 3.2 Gen 2 USB Type-C port (a 10Gbps port) on the rear panel, unless otherwise noted.

After we've run the tests defined below for external drives, we then format the drive to exFAT and run a couple of supplemental tests on a 2016 Apple MacBook Pro, testing over Thunderbolt 3 (if applicable) or USB Type-C. If the drive is a Thunderbolt 3-only drive, we run just the MacBook-based tests. In addition, we are in the process of adding a USB 3.2 Gen 2x2 card to our main storage testbed to accommodate the emerging class of external SSDs supporting that high-speed 20Gbps version of USB.

The Benchmarks: Internal SSDs

Here is a breakdown of the benchmark set we run on internal drives, whether M.2 "gumstick" drives or conventional 2.5-inch SATA internals. The drives are secure-erased between each run of the different tests.

PCMark 10 Storage

The main PCMark 10(Opens in a new window) Storage test from UL is an invaluable cutting-edge measure, providing a high-level view of how the drive will function under various everyday workloads, such as word processing and videoconferencing.

For internal SSDs, we first run the drives through the PCMark 10 Full System Drive benchmark, which simulates 23 different "traces" (simulated tasks) in the course of the run. The traces flex the drive in ways that approximate launching Adobe-based creative programs, booting up Windows 10, copying files, launching popular games, and more.

The overall score that PCMark 10 reports back represents how well a drive does throughout the entire PCMark 10 run. This score is the sanctioned score presented by UL's software at the end of each run. This score reflects a weighted average of the various activities that the PCMark 10 storage test simulates, a general indicator of how consistently a drive can perform through the 23 different usage scenarios.

It's a proprietary number, though, and is meaningful only when compared with scores of other, competing drives. That is where our reviews come in.

Getting Granular: Booting Windows 10 (PCMark 10 Trace)

We also dig into the more granular trace data that PCMark 10 presents. The first part of it we report is culled from the Windows 10 boot trace, which simulates a full operating-system startup procedure. The throughput number we report reflects how quickly the drive is able to feed the data required for that task set.

This and the following three PCMark 10-derived, trace-based tests represent a simulation of how quickly a drive is capable of feeding data when launching a particular program, copying files, or, in this case, booting Windows 10. PCMark 10 records how many megabytes per second the drive is reading what are known as "shallow-queue 4K random" blocks of data (i.e., of the kind in which most applications, games, or operating systems are stored). While UL recommends using the overall "read/write MBps bandwidth" metric in these tests, we dug a bit deeper to include only random 4K bandwidth in order to paint what we believe is a more specific picture of how well a drive can perform in these tasks.

Game Launching Tests (PCMark 10 Trace)

Next we report data from PCMark 10's traces around game launching. This again reflects how quickly a drive can read shallow-depth small random 4K packages. Note that the "4K" we're talking about here is file-block size(Opens in a new window), not file size; 4K is one of the more commonly used file-block sizes for game installations, though that composition does depend on the title you're playing.

While the three games tested in PCMark 10 are stored primarily in small random 4K, tests from around the web have shown that MMORPGs can more often use the 16K block size, and some games in other genres may tend to employ larger block sizes, from 32K up to 128K. However, for the sake of these tests, 4K small random read is the most accurate block-size metric relevant to these three popular FPS titles: Battlefield 5, Overwatch, and Call of Duty: Black Ops 4. We again report the read throughput for this kind of file.

Adobe Launching Tests (PCMark 10 Trace)

Next is the set of results based on traces simulating Adobe-application launches. As anyone who works regularly in programs like Adobe Premiere or Photoshop can tell you, a constant pinch point is the time it takes for these programs to launch.

Mind you, our results don't tell the whole story of how a drive will perform for all creative applications. Depending on the complexity of your work and the number of elements in a scene, your software may have to load 3D models, sound files, physics elements, and more; in other words, more than just the program. Still, this is nonetheless interesting fodder for folks who live and breathe these Adobe apps.

Copy Tests (PCMark 10 Trace)

Finally in PCMark 10, we report on PCMark 10's traces that simulate file-copy actions. While at first these numbers might look low compared to the straight sequential-throughput numbers achieved in benchmarks like Crystal DiskMark and AS-SSD (below), that's due to the way this score is calculated and the nature of and differences between the source data. If you're regularly moving files around on your drive from one folder to another, this test is a handy relative throughput measure.

Crystal DiskMark 6

Beyond PCMark 10, we also use the venerable Crystal DiskMark(Opens in a new window) utility for a second opinion on throughput. Crystal DiskMark's sequential-read tests measure read/write activity with data written in a large contiguous block on the drive, which is similar to how manufacturers themselves test drives to advertise their performance. These tests represent a "best case," straight-line scenario for file transfers.

We also use Crystal DiskMark's 4K tests to measure random reads/writes, which reflect data activity in which the drive is fetching and writing scattered files and pieces of files across the drive. This is mostly just used as a reality check against the wealth of 4K read data culled from PCMark 10's traces.

AS-SSD

AS-SSD(Opens in a new window) is a popular utility designed specially for testing SSDs. We use AS-SSD's unique copy tests to simulate moving different types of files around on the drive. This is similar to the folder drag-and-drop test that we use for external drives (detailed below), but it's more comprehensive since AS-SSD offers three different transfer tests: a sample game-install folder, a program folder, and a single big ISO file.

In this test, AS-SSD makes a copy of the given file to another folder on the test drive. This is telling because some drives handle single large files (like the ISO) better than bunches of smaller files (like the game install folder).

The Benchmarks: External SSDs

As noted, in testing we attach external SSDs to the native USB 3.2 Gen 2 port on our main Windows 10 testbed, and afterward (if relevant) to a Thunderbolt 3/USB Type-C port on our test MacBook Pro. With the Windows 10 machine, we'll cite if a drive is attached instead to the expansion-card USB 3.2 Gen 2x2 port on our Windows 10 testbed.

PCMark 10 Data Drive Benchmark

We're not done with PCMark 10 quite yet! The Data Drive Benchmark is a solid test to run on any drive you intend to use as a data archive or a backup drive, and typically takes between 10 and 30 minutes to run, depending on the drive type and its connection standard.

Like the PCMark 10 Storage test, it runs through a host of trace-based activities to simulate typical daily drives activities for a secondary drive. The proprietary number it reports back is useful only when compared against other drives' PCMark 10 results.

Crystal DiskMark 6

For external SSDs, we run the Crystal DiskMark 6 test under the same parameters as for internal drives above (sequential read/write, and 4K read/write).

BlackMagic Disk Speed Test

With this and our next test, we move the drive, if compatible, over to our Apple MacBook Pro tester platform and reformat it into exFAT. We use the macOS-only BlackMagic Disk Speed Test(Opens in a new window) app from professional media software firm BlackMagic Design (the makers of DaVinci Resolve) to perform this test. It reports back a drive's throughput in bits per second. This utility is typically used to discern whether a given drive has enough throughput to play back specific video formats smoothly. But it also returns some useful throughput measurements.

BlackMagic offers both a read score and a write score, which we compare with those of other, similar drives. These scores are useful in discovering the theoretical maximum speed that a drive can achieve.

Folder Transfer Test

The final test for external drives is a drag-and-drop test, also performed on our MacBook Pro. It uses the macOS Finder to copy a 1.23GB test folder full of several different file types from the testbed's internal drive to the external SSD being tested. We hand-time the scores (in seconds).