FAQ & Troubleshooting

If you run CrystalDiskMark with Administrator rights, it does not show network drives. To benchmark a network drive (mapped drive or UNC path), run CrystalDiskMark without Administrator rights.

UAC dialog:

• Click Yes → runs with Administrator rights → network drives are hidden.
• Click No → runs as standard user → network drives can be selected.

Results can vary for several reasons:

• Test data: Some SSDs perform differently with random data vs. zero-filled (0fill) data. CrystalDiskMark can use different test data; other tools may use 0fill only.
• Test file size and position: Where the test file is placed on the drive and how large it is can affect throughput.
• Fragmentation: Disk fragmentation can change results on HDDs and some SSDs.
• Controller and CPU: IDE (PATA), SATA, RAID, SCSI, or NVMe controller and CPU speed can all influence results.

So it is normal to see different numbers between CrystalDiskMark and other tools. Use the same tool and settings when comparing drives.

This often means the program does not have enough rights to create the test file on the selected drive. Run CrystalDiskMark as Administrator (right‑click → Run as administrator, or click Yes at the UAC prompt). Note: running as Admin will hide network drives; for local drives, Admin usually fixes “failed” or “access denied” errors.

Default is 1 GiB, which is fine for most SSDs and HDDs. For slow storage (e.g. USB 2.0 flash drives, old HDDs, or network drives), use a smaller size (e.g. 64 MiB or 128 MiB) so the test finishes in a reasonable time. For high-end NVMe drives, 1 GiB or larger can stress the drive more and may show sustained performance; very large sizes (e.g. 32 GiB) take longer and use more free space.

Rule of thumb: ensure the drive has enough free space for the test file (at least the test size you select).

Local drives (C:\, D:\, etc.): If the benchmark fails with “access denied” or cannot create the test file, run CrystalDiskMark as Administrator (right‑click → Run as administrator, or Yes at UAC).

Network drives: Run without Administrator rights (click No at UAC). If you run as Admin, network drives do not appear in the drive list.

Possible causes:

• Wrong drive or partition – Make sure you selected the SSD, not an HDD or network drive.
• SATA vs NVMe – SATA SSDs are limited to about 550 MB/s. If you expected NVMe speeds, check that the drive is NVMe and in an NVMe slot.
• PCIe link speed – Some slots or BIOS settings run at PCIe x2 or Gen3 instead of x4/Gen4. Check BIOS and that the drive is in the correct M.2 slot.
• Background activity – Antivirus, Windows Update, or other apps can slow the test. Close them and run again.
• Drive nearly full or SLC cache exhausted – Some SSDs slow down when the cache is full or when the drive is almost full. Free space and a second run can help.

Use the main menu: File (or equivalent) usually has options such as Copy (to clipboard as text) and Save as Image (screenshot of the results). Exact labels may vary by edition and version. After copying, you can paste into a forum, document, or spreadsheet.

It depends on the test size, number of runs, and drive speed. With default settings (e.g. 1 GiB, 5 runs), a fast NVMe SSD might finish in one to three minutes. A slow HDD or USB drive can take much longer. Use a smaller test size (e.g. 64 MiB or 128 MiB) if you want a quick result on slow storage.

Yes, for occasional use. The benchmark writes and reads test files, which uses some of the drive’s write endurance. Running it once or a few times is fine. Running it constantly for hours every day could shorten an SSD’s lifespan over time. For normal benchmarking (e.g. after a new install or when comparing drives), you do not need to worry.