1. A method for metadata management in a storage system, comprising: using a computer or processor to perform the steps of providing a least recently used (LRU) queue of a maximum size, the LRU queue configured for holding metadata for a maximum number of sub-LUNs; determining whether the metadata for a particular sub-LUN is held in the LRU queue when the particular sub-LUN is being accessed; updating the metadata for the particular sub-LUN and moving the updated metadata to the head of the LRU queue when the metadata for the particular sub-LUN is held in the LRU queue; inserting the metadata for the particular sub-LUN to the LRU queue when the LRU queue is not full and the metadata for the particular sub-LUN is not held in the LRU queue; replacing a last entry in the LRU queue with the metadata for the particular sub-LUN and moving that entry to the head of the LRU queue when the LRU queue is full and the metadata for the particular sub-LUN is not held in the LRU queue; and controlling the number of sub-LUNs in the storage system to manage an amount of data accessed within a range of sub-LUNs including the particular sub-LUN with respect to an amount of available data storage within the range of sub-LUNs including the particular sub-LUN.