Keep in mind that when you recommend this drive to members of the Homegroup, it is specifically made available via File History. In other words, you will not see the drive as a shared device in the Homegroup or in Network. While you won't see the drive in Network, you will find a new share called FileHistory#. Even though you can see and access the share, you shouldn't try to use it as a traditional share i.e. you should not copy, move, or delete files. If you do, chances are good that you will corrupt the File History management system.
How it works
Once you have File History up and running it is ready to begin protecting your data. By default, every hour File History will go to work and create backup copies of any file that has changed since the last backup. To do so, File History takes advantage of a feature of the NTFS file system, called the Change Journal.
Essentially, when any change is made to a file or folder on your hard disk, the change journal is updated with a description of the change and the name of the file or folder. So, in order to determine which files need to be backed up, File History simply consults the NTFS change journal, discovers which files or folders have changed, and backs them up. Using the change journal is fast and efficient and won't suck up tons of system resources like running a conventional backup routine does.
File History has some other cool features up its sleeve as well. If the device configured as the backup location becomes unavailable, such as when a USB cable is disconnected or network goes down for maintenance, File History will continue to do its job by saving the copies to a cache on the local drive. Once the backup location becomes available again, the cached contents are transferred to the backup location and removed from the local drive.
In addition, File History is sensitive to resource utilization. In other words, if File History is running and some other task needs the same system resources, File History will automatically back off and go into an idle state as it waits for the other task to finish before it resumes.
File History is also aware of activity related to mobile computing such as running on AC or battery power or when the system goes into Sleep mode and will adjust accordingly so as not to interfere with power saving features.
As I mentioned, File History will scan through the change journal every hour and back up changed files. However, you can change that frequency as well as adjust other settings. To do so, select the Advanced setting in the Task pane on the left side of the main window. You'll then see the Advanced Settings window, shown in Figure G, and can change the various settings.
In the Versions section, you'll see the default settings but can change them to any of the available selections. For instance, you can set the Save copies of files setting, which is the frequency that File History will check for changes and make backups from 10 minutes to 24 hours. You can change the size of the offline cache from 5% to 20% of disk space, and you can change the length of time that File History will keep saved versions of changed files from one month to forever or until space is needed.
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