Files saved on a traditional (non SSD) hard drive are split into multiple fragments and are stored in different places on the hard drive. To read the file, the hard drive collects the pieces from the different areas, which can take time. You can run disk defragmentation which will try to rearrange the pieces of the file so that they are next to each other on the hard drive, which would improve read and write speeds.
If you’re running on a solid state drive, Windows won’t offer you the option to perform a disk defragmentation because it’s not necessary for SSDs.
To access disk defragmentation through the graphical user interface, look at the drive’s Properties and select the Tools tab. You’ll then see the option to Optimize and defragment the drive.
To run disk defragmentation from the command line requires that you use elevated permissions. So make sure you run the command line as administrator before you enter the command to peform a defragmentation which would be: defrag <volume>
For example: defrag C: