Windows 8 will Boot Faster than Previous Windows Versions, Microsoft Confirms

We designed Windows 8 so that you shouldn’t have to boot all that often (and we are always going to work on reducing the number of required restarts due to patching running code). But when you do boot we want it to be as fast as possible.

Qualitatively, people say they prefer to shut down because they want to have their PC completely “off” so that it uses no power – either to preserve battery life or to reduce their energy use. Hibernate is also a good option for this since it similarly has no power draw, and many people really like it. However, it’s clearly not for everyone, since one of the other things we’ve heard is that many people want to turn their PCs on and have it be a “fresh start” rather than running all of the stuff from their previous session. Sleep/resume is the best option for fast on/off transitions on today’s PCs, but it still consumes some power in order to preserve the contents of RAM, which means battery drain – even if it’s only a little bit on a well optimized system. All of this is happening with the backdrop of how we all use our mobile phones today, which is almost never restarting them, and always using what feels closest to a sleep-like state.

Our challenge then, was to design a way to meet all of these desires on today’s PCs without requiring some special new hardware. These were our goals:

• Effectively zero watt power draw when off
• A fresh session after boot
• Very fast times between pressing the power button and being able to use the PC.

In Windows 7 we made many improvements to the boot path, including parallel initialization of device drivers, and trigger-start services, but it was clear we’d have to get even more creative (and less incremental) if we hoped to get boot performance anywhere close to fast enough to meet all of these needs.

Our solution is a new fast startup mode which is a hybrid of traditional cold boot and resuming from hibernate.

In a traditional shutdown, we close all of the user sessions, and in the kernel session we close services and devices to prepare for a complete shutdown.

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).

It’s faster because resuming the hibernated system session is comparatively less work than doing a full system initialization, but it’s also faster because we added a new multi-phase resume capability, which is able to use all of the cores in a multi-core system in parallel, to split the work of reading from the hiberfile and decompressing the contents. For those of you who prefer hibernating, this also results in faster resumes from hibernate as well.

Another important thing to note about Windows 8’s fast startup mode is that, while we don’t do a full “Plug & Play” enumeration of all drivers, we still do initialize drivers in this mode. Those of you who like to cold boot in order to “freshen up” drivers and devices will be glad to know that is still effective in this new mode, even if not an identical process to a cold boot.

This new fast startup mode will yield benefits on almost all systems, whether they have a spinning HDD or a solid state drive (SSD), but for newer systems with fast SSDs it is downright amazing.

Of course, there are times where you may want to perform a complete shutdown – for example, if you’re opening the system to add or change some hardware. We have an option in the UI to revert back to the Windows 7 shutdown/cold boot behavior, or since that’s likely a fairly infrequent thing, you can use the new /full switch on shutdown.exe. From a cmd prompt, run: shutdown /s /full / t 0 to invoke an immediate full shutdown. Also, choosing Restart from the UI will do a full shutdown, followed by a cold boot.