Why is everybody keep mentioning to disable Fast Boot on Windows 8 if you have installed alongside Ubuntu? Is it something that is recommended only for UEFI machines or is it a suggestion for Legacy BIOS machines as well? Is it because it makes the Windows partition inaccessible from Linux or there is another more serious reason to disable it?
Fast boot explained with an image:
During fast boot the system loads the hiberfile and does not use the files on the filesystem.
So the biggest problem, and the worst problem you can have on a computer, is data loss: if you create a shared NTFS data partition the hibernation may maintain the file structure so if you try to save a file from Linux into the NTFS partition it will get lost on Windows reboot as it only remembers the old file structure. See this Ubuntu Forums thread for more information.
That alone is reason enough to never touch fast boot in a dual boot setup.
Two relevant discussions from Super User:
Hibernating and booting into another OS: will my filesystems be corrupted?
What do I have to take care of when hibernating both Ubuntu and Windows (dual-boot environment) Make sure to take note of this answer by Gilles.
In general: if a disc is mounted when using fast boot, Windows puts this disc and its content in a hiberfile. Any changes made to the system are gone when the hiberfile is restored. This includes mounted external discs. Ubuntu will refuse to mount a disc that has a hiberfile.
One of the bad messages you see in these topics is getting a "disc has errors" when booting Windows.
