Windows – Running Windows disk defragmentation on boot in Windows 10

Measuring the performance gain from defragmentation is rather difficult, however there are some utilities that are meant to "aid" you with it.

There's the utility called File Access Timer, from Raxco, available here. This tool will read a certain file/folder a set amount of times and display how long it took, along with the fragments.

Excerpt from the readme

The File Access Timer allows you to select a file or folder and read the contents several times in order to measure the performance gain achieved through defragmentation. The general process is to select a fragmented file, read the file using Raxco's File Access Timer, defragment the file, and re-measure the time needed to read the file. By doing this you can see the benefits of defragmentation for yourself.

Defrag is a Windows program and runs while Windows is running. You can schedule a scan disk for before Windows completely loads, but not defrag. There are tools you can use that defragment outside of Windows, but Windows' built-in defrag is more than sufficient for most needs.

I schedule defrag to run for a few hours a couple of nights each week. That way it keeps the disk to a very low level of fragmentation.

Regarding the -b option, I found this explanation: http://www.edbott.com/weblog/2003/04/beware-of-bogus-xp-advice/

The Prefetch directory has one additional salutary function when used in conjunction with the built-in defragmenting tool. Every three days, during idle times, this utility rearranges program code, moving it to the outside of the disk to make it more efficient when loading (to force Windows to perform this optimization without having to do a full defragmentation, use the Defrag.exe command with the -b switch. For instance: defrag c: -b).

Apparently your computer already does this regularly, and unless you move massive files frequently across your hard disk drive and restart several times each day, you're not going to notice must of a benefit.

In my experience, people turn to defrag to speed up their systems much too quickly. I can count on one hand the times defragging has actually sped up systems that I have observed. And as a veteran of corporate and consumer IT support, that's saying something.

Set a scheduled defrag, don't bother with the -b option, and leave it at that. If you have computer slowness there are a myriad other options you should look into that will be much more effective in speeding the system up.