In one embodiment, the storage system maintains a plurality of usage records corresponding to a plurality of logical file system namespaces representing one or more directories each having one or more files, each file being stored in the storage system as a plurality of segments in a deduplicated manner. In one embodiment, the storage system identifies a first set of the usage records corresponding to a first of the file system namespace, wherein the first set of usage records contains information of logical and physical storage space used by one or more of the file system namespaces. According to one aspect of the invention, the storage system determines a percentage of the storage system available to the first file system namespace based on the first set of usage records and a provisioned percent quota.