The GlusterFS native driver of the File Share Service allows users to create shares of specified sizes. If no Red Hat Gluster volumes of the exact requested size exist, the driver chooses one with the nearest possible size and creates a share on the volume. Whenever this occurs, the resulting share will use the entire volume.
For example, if a user requests a 1GB share and only 2GB, 3GB, and 4GB volumes are available, the driver will choose the 2GB volume as a back end for the share. The driver will also proceed with creating a 2GB share; the user will be able to use and mount the entire 2GB share.
To work around this, implement File Share quotas for users. Doing so will prevent them from provisioning more file share storage than what they are entitled to.