Engineering Explained: Windows 10 Restart Versus Shutdown

January 10, 2021

A long time ago–in the bad old days–when people were done using their computer they’d reach over and throw the power switch, which would make a big “thunk”. This sound would reverberate through the entire computer, and through the room where the computer sat, to let the computer know it was time to stop working. Times were simpler then, that’s for sure.

Now, with modern Windows computers we have to go through a complicated dance of clicking buttons, waiting for processes to stop, and watching boring graphics appear on the boring screen made by boring interface designers leading boring lives. But, outside of the boring window dressing, do you know what really happens when you click the shutdown button? For that matter, do you know what really happens when you click the restart button? Is there a difference? That’s what we’re here to demystify.

In order to understand the differences better, we have to go back. Way back. We have to go back to the land of cloud backgrounds and FAT32. In early versions of Windows, clicking the restart button was not a lot different from clicking the shutdown button. If a user clicked the shutdown button, in say Windows 98, the computer would simply shutdown. During that process Windows would do a lot.

  1. It would check to see if any other users were logged-in or running processes on the computer.
  2. It would stop any user processes that were running by sending a shutdown signal to each one so they could take the chance to end gracefully.
  3. Once all the user processes are stopped, it would log out the current user.
  4. It would then start closing its own services and turn itself off bit-by-bit.
  5. Finally, it would send the shutdown signal to the power management hardware to turn off.

But, if the user were to click reboot it would spring right back to life after going through the whole shutdown process. Either way, all running processes would stop, files would be put to rest to negate corruption, and the operating system would completely halt. Before 1996 there was one extra step where the user would have reach over and press the power button to turn the system off, because we didn’t yet have the Advanced Configuration and Power Interface (ACPI) standard that allowed our software to control a device’s power. Man, have we come a long way… 

With modern operating systems like Windows 10, there are a few differences that matter. Today if a user clicks shutdown it is not like a restart. If a user clicks shutdown now, Windows 10 actually goes into a state of deep hibernation. Just like in earlier versions of Windows: processes are stopped, users are logged out, and unneeded services are turned off. But, this is where the similarities end. Once Windows reaches this point, only some drivers and the Kernel is running. That is when Windows alerts the remaining device drivers that it is going into hibernation and to prepare for it. It then saves the current system state and writes it out to a hibernation file. Finally, it turns off the computer.

This whole process is called Fast Startup and has been around since Windows 8. On the other hand, when a user clicks restart the restart process is still followed like normal. Everything is cleared. Memory is cleared and nothing is written to disk. That is why a restart is better when installing and applying updates or trying to clear up any issues a user may have with modern Windows. 

But, there might be some reasons to disable Fast Startup, which is enabled by default.

  1. If you use mounted disk images that are encrypted with a third-party, full-disk encryption application like TrueCrypt, Fast Startup might cause some issues with those disks being automatically re-mounted after a shutdown. Keep in mind, Fast Startup does not impact boot disks that are encrypted with TrueCrypt. BitLocker, naturally, is also not affected.
  2. When you shut down a computer with Fast Startup enabled, Windows locks the startup disk. That means you won’t be able to access the disk from other operating systems. If you have dual-boot enabled or try to look at the disk from another operating system, it will look almost as if it is encrypted. If anything is changed, it can corrupt your Windows installation.
  3. Some users might not be able to access their BIOS/UEFI settings when the computer is shutdown with Fast Boot enabled. Due to the hibernation state that Windows goes into, the system may not go into a fully powered-down state. That is where the issue lies. 

Given what we now know, we can see that performing a shutdown is not like performing a restart in Windows 10. If you have a user that is having issues with their Windows 10 system, an Engineer would not want to recommend a shutdown with modern hardware. A restart would be the way to go. Fast Startup is a great feature to include in Windows, but it led to some unforeseen consequences. One take away is feel free to disable the feature. People hardly shutdown their computer anymore and disabling Fast Startup will not break anything. Plus, anyone using an Solid State drive likely won’t see a huge speed gain or loss from having the feature disabled. So, tell us what you think in Discord, enable or disable? Do you see a difference?

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