DriveFiller is a simple open-source application that fills your drive and has customizable file sizes.
It can be used as a "benchmark", you can see the time it takes to finish writing a file (measured in milliseconds).
There's also the option to log everything into a .log file.
.NET 6.0 SDK is required to build the project: https://dotnet.microsoft.com/download/dotnet/6.0
This project is licensed under the GNU General Public License version 2 ("GPLv2") and therefore can be used in commercial projects. However, any commit or change to the main code must be public and there should be a copyright notice in the source code clarifying the license and its terms as part of your project as well as a hyperlink to this repository. This program is distributed in the hope that it will be useful. Read more about GPLv2.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.