The Windows 8 team has posted a bit on the new Windows 8 boot time optimization. One of the major factors in judging a PC’s speed is it’s boot time, and Windows 8 looks to make some huge increases in speed. I have upgraded to an SSD on my main Windows 7 machine and am very happy with my boot speeds, I would love to test out Windows 8 (hopefully a public beta soon) booting from the same SSD.

Now here’s the key difference for Windows 8: as in Windows 7, we close the user sessions, but instead of closing the kernel session, we hibernate it. Compared to a full hibernate, which includes a lot of memory pages in use by apps, session 0 hibernation data is much smaller, which takes substantially less time to write to disk. If you’re not familiar with hibernation, we’re effectively saving the system state and memory contents to a file on disk (hiberfil.sys) and then reading that back in on resume and restoring contents back to memory. Using this technique with boot gives us a significant advantage for boot times, since reading the hiberfile in and reinitializing drivers is much faster on most systems (30-70% faster on most systems we’ve tested).