Patent ID: 7155586

Claim:
A method of creating point-in-time view of data on a disk, comprising: initiating from a host, a first session of writing data to a disk which affects a portion of the disk; creating and storing entries in an array on the disk which identifies where the data written to the disk during said first session is located; initiating at least one second session of writing data to a disk at a time different from the initiation of the first session, with said at least one second session of writing data affecting a portion of the disk; copying data in any portion of the disk corresponding to said first session which is to be affected by a write operation by said at least one second session; creating and storing entries in said array which identify where data corresponding to said first session which is to be affected by a write operation by said at least one second session is located; invalidating said entries in said array for said at least one of said first and said second session when at least one of a new first session and a new second session is initiated; and wherein said first session and said at least one session are initiated and controlled by a first host, and point-in-time viewing of the data on the disk is conducted by a second host.