Patent ID: 8285758

Claim:
A method of operating a file server, said method comprising the steps of: configuring slices of data storage from different classes of the data storage, each class of the data storage having respective performance and cost characteristics for storage and retrieval of data, in order to obtain at least a first configured slice of the data storage configured from a first one of the classes of the data storage, and a second configured slice of the data storage configured from a second one of the classes of the data storage; building a file system upon at least the first configured slice of the data storage and the second configured slice of the data storage so that the file system includes file system blocks allocated from the first configured slice of the data storage and file system blocks allocated from the second configured slice of the data storage; and allocating the file system blocks of the file system to at least one file in the file system based on the storage class of the file system blocks in accordance with at least one storage allocation policy; wherein a data storage object in the file system is migrated from one of said classes of storage to another while read and write access to the data storage object is maintained in order to move the data storage object to a different class of storage that is more cost effective for a required level of performance, and wherein the file system stores a production file system or logical unit number (LUN) of storage and also stores snapshot copies of the production file system or LUN, and the snapshot copies are evacuated from selected storage devices and the selected storage devices are removed during a lifecycle of the snapshot copies.