Methods for creating hierarchical copies

A method for copying a logical volume in a data storage system, comprising:

• forming a first logical volume;
• storing data belonging to the first logical volume in physical storage of the data storage system;
• receiving a first command to copy the first logical volume to a second logical volume;
• executing the first command by forming meta-data that designates the first logical volume as a first superior volume of a meta-volume and that designates the meta-volume as a second superior volume of the second logical volume;
• receiving a second command to access data in the second logical volume;
• executing the second command by using the meta-data to access the data in the data storage system;
• receiving a third command to access the data in the first logical volume;
• and
• executing the third command by accessing the data in the data storage system independently of the meta-data;
• receiving a fourth command, subsequent to the first, second and third commands, to copy the first logical volume to a third logical volume;
• executing the fourth command by altering the meta-data to form modified meta-data that designates:
• the first logical volume as a third superior volume of a further meta-volume;
• and
• the further meta-volume as a fourth superior volume of the meta-volume and as a fifth superior volume of the third logical volume;
• receiving a fifth command, subsequent to the fourth command, to access the data in the first logical volume;
• executing the fifth command by accessing the data in the data storage system independently of the modified meta-data;
• receiving a sixth command, subsequent to the fourth command, to access the data in the second or third logical volumes;
• executing the sixth command by using the modified meta-data.