A sub-volume, like a storage volume, is a physical location on a server, to which reports can be archived and from which documents can be retrieved. A sub-volume is a subdivision (that is, a subdirectory) of a storage volume.

When you first archive reports into a volume, the reports are automatically stored in the first sub-volume. (Initially, volumes contain only one sub-volume.) If you promote the sub-volume, or if the sub-volume is automatically promoted — for example, when the maximum sub-volume size (specified on the Storage Group page) is reached — the first sub-volume is closed and a second sub-volume is opened. Reports will be archived to this second sub-volume until it is promoted too.

A new sub-volume may be created on any volume of the same type (First Copy or Second Copy), which is contained in the storage group. The system selects the first volume, which has enough space for creating another full sub-volume. 

Volumes can contain an unlimited number of sub-volumes. The only limiting parameter is the volume size (specified on the Storage Volume page when adding a volume). Once the specified maximum volume size is reached, no additional sub-volumes can be opened on that volume.

A storage volume may be closed by an administrator to prevent further writing.

You can view detailed information about the storage group's sub-volumes on the Sub-Volumes Information tab.