Analyzing sub-lun granularity for dynamic storage tiering

A method for metadata management in a storage system, comprising:

• using a computer or processor to perform the steps of
• providing a metadata queue of a maximum size, the metadata 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 metadata queue when the particular sub-LUN is being accessed;
• updating the metadata for the particular sub-LUN when the metadata for the particular sub-LUN is held in the metadata queue;
• inserting the metadata for the particular sub-LUN to the metadata queue when the metadata queue is not full and the metadata for the particular sub-LUN is not held in the metadata queue;
• replacing an entry in the metadata queue with the metadata for the particular sub-LUN when the metadata queue is full and the metadata for the particular sub-LUN is not held in the metadata 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.

A storage system configured for supporting sub-LUN tiering, comprising:

• a higher performing tier;
• a lower performing tier;
• a metadata queue of a maximum size for holding metadata for a maximum number of sub-LUNs;
• a metadata queue controller configured for managing the metadata held in the metadata queue and identifying at least one frequently accessed sub-LUN for moving to the higher performing tier, wherein the at least one frequently accessed sub-LUN is identified based on the metadata held in the metadata queue;
• a metadata queue adjustment module configured for determining a utilization level of the higher performing tier and adjusting the size of the metadata queue based on the utilization level determined, where the number of sub-LUNs in the storage system is controlled to manage an amount of data accessed within a range of sub-LUNs including a particular sub-LUN with respect to an amount of available data storage within the range of sub-LUNs including the particular sub-LUN.