For a quick built-in check, run WinSAT from Command Prompt or PowerShell: winsat disk -seq -read -drive c tests sequential reads on C:, while winsat disk -ran -read -drive c tests random reads. Replace c with the drive letter you want to assess, without a colon. For more control over the workload and output, Microsoft DiskSpd can run a read-only test against a file on the SSD.
Choose a command-line test
| Tool | Best for | What you can control | Target |
|---|---|---|---|
| WinSAT | A quick built-in Windows disk assessment | Sequential or random access; read or write | Drive letter or physical disk number |
| DiskSpd | A configurable storage workload | Block size, access pattern, threads, queue depth, duration, warmup, caching, and output | File path, drive letter, or physical device ID |
Start with reads. WinSAT requires one access mode (-seq or -ran) and one operation (-read or -write). DiskSpd has many more workload controls, and Microsoft warns that a write test can destroy existing data without warning. The commands below are read-only.
Run a quick SSD check with WinSAT
- Open Command Prompt or PowerShell. For a disk assessment, run the command in a terminal window; if Windows denies access, reopen the terminal as an administrator and retry.
- Run one of the following, replacing
cwith the drive letter to check:winsat disk -seq -read -drive c— sequential reads.winsat disk -ran -read -drive c— random reads.
- Wait for WinSAT to finish, then review the results it prints. Treat them as an assessment of the selected workload, not as a universal SSD score or a guarantee of application performance.
WinSAT also documents selecting a physical disk number with -n <disk number> instead of -drive <letter>. Its documented syntax includes optional XML output, iteration counts, operation counts, and I/O sizes; the Microsoft reference is for older Windows releases, so verify those options on your own Windows version if they behave differently. Microsoft’s WinSAT disk command reference documents the syntax and examples.
Run a configurable read test with DiskSpd
Microsoft DiskSpd is a Windows storage performance tool with precompiled binaries available from its releases. The project lists DiskSpd 2.3, dated September 3, 2026. Its binary release supports Windows 10 version 1803 or later. IoRing and BypassIO options require Windows 11 or later; BypassIO also requires NTFS and read-only unbuffered operation.
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Prepare a file target
Use a dedicated test-file location on the SSD you want to assess, and make sure it has at least 2 GiB of free space for the example below. A file target exercises the filesystem and storage stack as well as the device. DiskSpd also accepts drive-letter and physical-device targets, but direct-device testing is more specialized and is not the safer beginner option.
Run the read-only command
In Command Prompt or PowerShell, run:
diskspd -c2G -b4K -F8 -r -o32 -W5 -d10 -Sh C:ssd-test.dat
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This is a short random-read example adapted from Microsoft’s documented sample, not a universal preset. The options mean:
-c2G: create a 2 GiB test file at the target path.-b4K: use 4 KiB I/O blocks.-F8: use eight total threads.-r: use random rather than sequential access.-o32: allow 32 outstanding I/O operations.-W5: warm up for five seconds before measuring.-d10: measure for ten seconds.-Sh: use the documented unbuffered/write-through combination.
There is no -w option in this command, so it runs a read workload; DiskSpd’s parameter reference says the default without a write percentage is 100% reads. The command still creates the target file. Keep the path on the SSD being tested, and do not substitute a raw device target unless you understand the risks.
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Understand the sample and safety boundary
Microsoft’s examples include a sequential read command, diskspd -c2G -b4K -o1 -W60 -d60 -Sh testfile.dat, as well as random, sequential, serial, concurrent, read, and write workloads. The example above uses shorter warmup and measurement periods and different concurrency settings, so its result is not directly comparable to that longer sample.
Do not run a DiskSpd write workload casually or copy a write sample without understanding its target. Microsoft’s current parameter documentation states: “IMPORTANT: a write test will destroy existing data without a warning.”
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Interpret the results fairly
A sequential throughput result and a random-I/O result describe different kinds of work. DiskSpd results also change with block size, thread count, queue depth, test duration, warmup, caching mode, and target type. Save the full command line with the output so you know what workload produced it.
- When comparing two runs, use the same tool, target type, access pattern, block size, concurrency, duration, and caching mode.
- Do not compare a WinSAT result directly with a DiskSpd result as if both were the same test.
- Do not assume the result should match an SSD manufacturer’s advertised peak. The Microsoft sources document test controls and syntax, not universal consumer SSD pass/fail thresholds or representative expected speeds.
Sources and version scope
WinSAT disk command reference is labeled as a previous-version reference for Windows Vista through Windows 8; current behavior for every Windows release is not established here. For DiskSpd, see the official project repository, its release page, the command-line parameters, and sample commands.
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