Cloning technique for efficiently creating a copy of a volume in a storage system

A system adapted to efficiently creating a copy of a parent virtual volume (vvol) in an aggregate of a storage system, the system comprising:

• disks coupled to the storage system and configured to store information served by the storage system;
• a file system executing on the parent vvol of the storage system, the file system logically organizing the information as a structure of files and blocks on the disks;
• a base snapshot sharing a parent container file represented as a parent buffer tree having a plurality of blocks in the aggregate, the plurality of blocks including level 0 data blocks that comprise all blocks used by the parent vvol, wherein one of the level 0 blocks is a snapshot volinfo block, the base snapshot sharing data structures with the file system executing on the parent vvol;
• and
• a clone comprising a clone container file represented as a clone buffer tree having a plurality of blocks in the aggregate, the plurality of blocks including level 0 data blocks comprising all blocks used by the clone, wherein the clone container file initially contains only a modified volinfo block stored in one of the level 0 blocks, the modified volinfo block being a modified version of the snapshot volinfo block, wherein the modified volinfo block forms a root of a modified volinfo block buffer tree that is similar to a parent volinfo block buffer tree of the parent vvol such that all blocks of the parent volinfo block buffer tree are accessible when traversing the modified volinfo block buffer tree.

Apparatus for efficiently creating a copy of a parent virtual volume (vvol) in an aggregate of a storage system, the apparatus comprising:

• means for providing a base snapshot of the parent vvol;
• means for creating a new vvol embodied as a clone, the clone comprising a container file;
• means for modifying a volume information (volinfo) block for the clone, the modified volinfo block comprising a modified version of a volinfo block from the base snapshot;
• and the modified volinfo block points to one or more blocks of parent vvol;
• means for writing the modified volinfo block to the container file;
• and
• means for instantiating the clone to service storage requests directed to the storage system by loading a file system associated with the new vvol onto the clone, and bringing the clone online, with the clone owing only the modified volinfo block.

A computer readable medium containing executable program instructions for efficiently creating a copy of a parent virtual volume (vvol) in an aggregate of a storage system, the executable instructions comprising one or more program instructions for:

• providing a base snapshot of the parent vvol;
• creating a new vvol embodied as a clone, the clone comprising a container file;
• modifying a volume information (volinfo) block for the clone, the modified volinfo block comprising a modified version of a volinfo block from the base snapshot, and the modified volinfo block points to one or more blocks of the parent vvol;
• writing the modified volinfo block to the container file;
• and
• instantiating the clone to service storage requests directed to the storage system by loading a file system associated with the new vvol onto the clone, and bringing the clone online, with the clone owning only the modified volinfo block.

A method, comprising:

• organizing a parent virtual volume within an aggregate, where the aggregate includes a plurality of disks;
• providing a base persistent consistency point image (PCPI) of the parent virtual volume;
• creating a new virtual volume within the aggregate, where the new virtual volume is embodied as a clone, the clone comprising a container, wherein the clone is a read write copy of the parent virtual volume;
• generating a volume information (volinfo) block for the clone called a clone volinfo block, wherein the clone volinfo block is a modified version of a PCPI volinfo block and the clone volinfo block points to one or more blocks of the parent virtual volume and one or more changed blocks in the clone;
• and
• instantiating the clone to service storage requests directed to a storage system.

A storage system, comprising:

• an aggregate including a plurality of disks, where the disks store information served by the storage system;
• a parent virtual volume stored within the aggregate;
• and
• a clone comprising a clone container, wherein the clone container initially contains a clone vol info block, wherein the clone volinfo block allows shared access to blocks used by the parent virtual volume when the clone was generated and one or more changed blocks of the clone, wherein the clone is a read write copy of the parent virtual volume.