[Someone1234]

I don't understand how that is technologically possible.

Most of Windows 10's boot, when Fast Startup is enabled, doesn't involve the typical system folders at all. Effectively when you shut down, they collapse the userspace, and store the kernel/services/etc into the hibernation file. When you "boot" the computer, the hibernation file is re-mapped into memory sequentially, and the user is prompted to login.

Compacting the OS definitely saves space. But I don't understand how it would reduce boot times from a technical perspective, since IO isn't even reading those folders during a default boot on Windows 10.

[Alupis]

You're not always "fast booting" windows 10. When you restart/reboot, for example, it must read all those files from the disk.

You'll get a performance boost by reading compressed data off the (slow) disk and expanding it in (fast) memory.

This can effectively increase read speeds greatly (reading a 2mb file off disk but it expands to 3mb's for example, that 3rd mb came almost "for free").

[anonymfus]

>Most of Windows 10's boot, when Fast Startup is enabled[...]

You are completely right for this case.

[Someone1234]

This case is the default for Windows 10.