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The disk space used by the Server is in C:\AD by default. The Vault (in the AD directory) is where the latest copies are kept, in addition to past versions and deleted files, up to the space specified by the threshold. The auto-cleanup deletes oldest version of files until the used space falls below the set threshold. The cleanup only affects old versions of files and deleted files; current files are not deleted.
To manage disk space
In the Windows Task bar, double-click the Server icon
.The Server Console appears.

In the Disk usage/Auto-cleanup threshold area, the size of the disk and total disk space currently in use are displayed.
Used now displays the size of your entire disk, and the total amount of the disk that is currently used for any reason. The Server can be a small or large part of this total, depending on what else you have on the disk. To move the space that the Server uses to a different device, open the Server Parameters dialog box.
Threshold allows you to determine how much disk can be used before the Server runs its auto-cleanup operation on the Vault. It is not a good idea to keep the threshold bar so close to the used bar that cleanup happens very often.
Adjust the threshold after which automatic cleanup should take place. Move it as far to the right as you can afford in drive space.

You can force a cleanup at any time by moving the Threshold bar to the left of the Used now area, thus allocating less space than is currently used and forcing the Server to delete files. This may slow performance of the Agents for a few minutes as files are cleaned up.
Housekeeping is idle means that no cleanup is in progress.