Maintaining a percentage of unallocated storage capacity in a disk group is a useful means of managing online storage to avoid application failures. When an application requires more storage, its volumes can be extended quickly and easily by a system administrator while it's online, using the unallocated capacity. If volume expansion causes unallocated capacity to drop below a safety threshold, the event can be displayed in the GUI provided with SFW. Additional storage should then be installed and added to the disk group to maintain an adequate cushion for anticipated application requirements.