An article at h-online.com warns users of dual boot systems with Windows 8 Fast Startup that they risk data loss:
The Fast Startup feature creates an issue because it doesn't shut Windows 8 down completely but switches it to a special hibernation state instead â€“ although it looks like it has been freshly booted when switched back on because all applications have been closed. However, for the Fast Startup feature's hibernation state, Windows 8 will store Windows session information â€“ such as the cache with the current filesystem state of any mounted FAT and NTFS partitions â€“ in a memory image that is restored during Fast Startup.
This can easily cause data loss when other operating systems are used to write to these partitions: after waking up, the supposedly powered-down, but actually hibernating, Windows will resume operation with now obsolete data and filesystem information. The risk exists not only when Linux is installed on disk in parallel, it also arises with any other type of access â€“ such as that from the Windows-7-based Windows PE 3.0 or from recovery systems that are booted from a CD or USB flash drive.