CrystalDiskMark is a free disk benchmark for Windows that measures how fast a drive reads and writes data. It runs on x86, x64 and ARM64 systems and works with hard drives, SSDs, USB memory and network drives. Crystal Dew World releases it as open source under the MIT License.
How a benchmark run works
Before starting, you choose the drive, the test file size and how many times each test repeats. CrystalDiskMark writes a test file of the chosen size to that drive. It runs its read and write tests against the file and reports a result for each row. The “All” button runs the full set, and each test can repeat from 1 to 9 times.
Test file sizes range from 16 MiB up to 64 GiB. The default of 1 GiB can take a long time on slow storage such as USB memory, so a smaller size suits those devices better. The tests themselves run through the DiskSpd engine.
Sequential and random tests
Each result row combines an access pattern, a block size, a queue depth and a thread count. Sequential tests move large blocks through the file in order, showing the transfer rate for big files. Random tests use small 4 KiB blocks at scattered positions.
Queue depth sets how many requests wait at once, and the thread count sets how many workers issue them. A deep queue shows performance under heavy load, while queue depth 1 shows the response to one request at a time. The default set in CrystalDiskMark covers both:
- Sequential, 1 MiB blocks, queue depth 8, one thread
- Sequential, 1 MiB blocks, queue depth 1, one thread
- Random, 4 KiB blocks, queue depth 32, one thread
- Random, 4 KiB blocks, queue depth 1, one thread
You can change each row’s block size, queue depth and thread count in the Settings dialog. CrystalDiskMark can show results in MB/s, GB/s, IOPS or average latency in microseconds.
Profiles and test modes
Ready-made profiles switch the whole test set at once. The NVMe SSD profile replaces the default rows with heavier loads, such as random 4 KiB tests with 16 threads. Other profiles include Peak Performance, Real World Performance, Flash Memory and Demo.
The Standard Edition adds Mix versions of the Default, Peak and Real World profiles, which add combined read and write tests. Read-only and write-only modes run just one direction.
Test data and accuracy
CrystalDiskMark can fill the test file with random data or with zeros. Some SSDs return different figures depending on this choice. Results also change with the test file size and position, fragmentation, the storage controller (SATA, NVMe, RAID and others) and CPU speed.
Each run writes data, so frequent benchmarks shorten the life of SSDs and USB memory. Results from different major versions are not comparable. Network drives appear only when CrystalDiskMark runs without administrator rights.
Saving and sharing results
You can copy a finished benchmark to the clipboard or save it as a UTF-16 text file. You can also save it as a PNG, JPEG or BMP image of the window. A comment field lets you add a note, such as the drive model, to the results.
Themes and editions
The interface supports many languages, zoom and font settings, and themes such as Dark, Flower and DarkRed. Besides the Standard Edition, Crystal Dew World offers Shizuku and Aoi Editions. These have themes built around its official characters, Suisho Shizuku and Suisho Aoi.
