Fast incremental backup method and system

A method for creating a logical storage unit-level archive of a set of logical storage units stored on at least one storage medium, the set of logical storage units (LSUs) comprising a plurality of LSUs, the method comprising:

• generating, by a processor in communication with the at least one storage medium, a first plurality of LSU descriptors, wherein each LSU descriptor from the first plurality of LSU descriptors describes a current version of one of the set of LSUs at about the time of the generating;
• reading, by the processor, from a first archive of the set of LSUs, a first archive plurality of LSU descriptors, wherein each of the first archive plurality of LSU descriptors describes a version of one of the set of LSUs when the first archive was created;
• comparing, by the processor, the first archive plurality of LSU descriptors with the first plurality of LSU descriptors;
• identifying, by the processor, a first LSU from the set of LSUs that has an associated LSU descriptor from the first plurality of LSU descriptors that does not match a corresponding LSU descriptor from the first archive plurality of LSU descriptors;
• and
• generating, by the processor, a second archive of the set of LSUs, wherein the second archive comprises the first file and the first plurality of LSU descriptors;
• and
• after generating the second archive of the set of LSUs, generating, by the processor, a third plurality of LSU descriptors, wherein each LSU descriptor of the third plurality of LSU descriptors describes a version of one of the set of LSUs at about the time of the generating;
• reading, by the processor, the first plurality of LSU descriptors from the second archive;
• comparing, by the processor, the third plurality of LSU descriptors to the first plurality of LSU descriptors;
• identifying, by the processor, a second LSU from the set of LSUs that has an associated LSU descriptor from the first plurality of LSU descriptors that does not match a corresponding LSU descriptor from the third plurality of LSU descriptors;
• and
• generating, by the processor, a third archive of the set of LSUs, wherein the third archive comprises the second file and the third plurality of LSU descriptors.