A method and system for allocating shared storage using one or more classification schemes is provided. One allocation method receives a storage request for provisioning storage from a class storage group configurable to share storage with more than one filesystems. Part of fulfilling this request includes associating a class and at least one corresponding storage allocation constraint with the storage request. The one or more storage allocation constraints can be used subsequently to determine if there is a sufficient amount of shared storage in the class storage group to fulfill the request. Accordingly, aspects of the present invention use at least one storage allocation constraint in determining if the storage allocation constraint for the class associated with the storage request allows allocation of shared storage to fulfill the request. When the storage allocation constraint allows, one implementation performs a provisioning of storage from the shared storage in class storage group.