Described are embodiments of an invention for allocating storage space in a storage system for critical data sets. The computing environment includes at least one server including a processor and memory. The server is coupled to storage. The memory further includes a storage manager including an allocation module and an alert module. The storage manager defines a common area for storing non-critical data sets and critical data sets in the storage group. The storage manager also defines a critical reserve area for storing only critical data sets in the first storage group. A predefined percentage of available storage space is reserved for the critical reserve area. The predefined percentage of available space is determined by comparing the available storage space within the critical reserve area to the storage space in the storage group. Upon allocating additional storage to the storage group, the allocation module allocates an amount of the additional storage space to the critical reserve area such that the predefined percentage of available storage space is maintained in the critical reserve area.