The Hibernate File in Windows is the disk space where memory data is stored when the computer is turned off. Because the location of the Hibernate File is determined very early in the boot process, it is tricky to defragment it. Well, tricky for all defragmenters except PerfectDisk that is, which is the only defragger that defragments the hibernate file, including the Windows built-in defragmenters.
In Windows Vista, 'Stand By' and 'Hibernate' have been combined into an additional 'Sleep' function which is active by default. When chosen, this new "Sleep" mode saves information from the computer's memory to the hibernation file on disk, but instead of turning off the computer, it simultaneously enters Standby mode. After a specified amount of time (3 hours by default), it shuts down (hibernates). If power is lost during Standby mode, the system resumes from the existing hibernate image on disk. Sleep mode, thus, offers the benefits of fast suspend and resume when in Standby mode and reliability when resuming from hibernation, in case of power loss.
The hibernate file -- another example of PerfectDisk's thoroughness.
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