This directive specifies the maximum number of bytes that can be written to the Volume. If you specify zero (the default), there is no limit except the physical size of the Volume. Otherwise, when the number of bytes written to the Volume equals size the Volume will be marked Used. When the Volume is marked Used it can no longer be used for appending Jobs, much like the Full status but it can be recycled if recycling is enabled, and thus the Volume can be reused after recycling. This value is
checked and the Used status set while the job is writing to the particular volume.

This directive is particularly useful for restricting the size of disk volumes, and will work correctly even in the case of multiple simultaneous jobs writing to the volume.

The value defined by this directive in the bareos-dir.conf file is the default value used when a Volume is created. Once the volume is created, changing the value in the bareos-dir.conf file will not change what is stored for the Volume. To change the value for an existing Volume you must use the update command in the Console.
