Patent ID: 8001327

Claim:
A computerized data storage system comprising: a plurality of storage volumes having multiple tiers, wherein tiers are set by characteristics of each storage volume; a communication interface operable to connect the computerized data storage system to at least one client requesting access to data in the storage system; a memory unit storing a volume table comprising an identifier for a volume and the tier information associated with the volume corresponding to the identifier, and a client table comprising client information and tier information associated with said client information; and a storage processor operable to: i. receive a data access request corresponding to a file from the at least one client; ii. determine the identity of the requesting client; iii. determine an original tier of the file; iv. determine a target tier to which the file should be migrated to, the determining a target tier being based on the identifier of the client and contents of said client table; and v. if the original tier and the target tier are different, migrate the file from the original tier to the target tier.