Patent ID: 9665436
Date: 2017-05-30
CPC Classifications: G06F

Claim:
1. A non-transitory computer readable article of manufacture comprising a storage medium having program instructions embodied therewith, said program instructions tangibly embodying computer readable instructions, the program instructions being readable and executable by a computer to cause the computer to perform a method for creating and managing snapshots of hierarchically managed logical volumes in a storage system, management of the snapshots being independent of migration status of the logical volumes, the storage system including first level storage and second level storage, the second level storage being lower than the first level storage, the method comprising: receiving a command for creating a snapshot of a logical volume; creating a management table for managing the snapshot of the logical volume, the management table including first metadata indicating creation status of the snapshot, second metadata indicating management status of data to be included in the snapshot, and third metadata indicating storage location of the logical volume, the storage location being either the first level storage or the second level storage, the first metadata, second metadata, and third metadata being separate and distinct data elements; detecting migration status of the logical volume; responsive to the logical volume being in the first level storage, creating a snapshot from the logical volume while the logical volume is in the first level storage, and updating the management table, the updating changing the first metadata to indicate that the snapshot of the logical volume has been created, changing the second metadata to indicate that the data in the logical volume is stored in the first level storage or is stored in both the first level storage and the second level storage, and changing the third metadata to indicate that the first level storage is the storage location of the logical volume; and responsive to the logical volume being migrated from the first level storage to the second level storage, updating the management table without recalling the logical volume from the second level storage to the first level storage, the updating changing the first metadata to indicate that creation of a snapshot is required, changing the second metadata to indicate that the data in the logical volume has migrated from the first level storage to the second level storage, and changing the third metadata to indicate that the second level storage is the storage location of the logical volume.