Patent ID: 7197665

Claim:
A method of protecting computer data, said method comprising the steps of: acquiring a first state snapshot S 1 of a first data volume consistent state at a time t 1 ; acquiring a second state snapshot S 2 of a second data volume consistent state at a time t 2 >t 1 ; generating a first precedent snapshot difference list S 21 comprising an identification of data blocks of said first state snapshot S 1 differing from data blocks in said second state snapshot S 2 ; creating a first precedent backup B 21 by copying from said first state snapshot S 1 data blocks identified in said first precedent snapshot difference list S 21 , said first precedent backup B 21 further comprising said first precedent snapshot difference list S 21 ; utilizing the first precedent backup B 21 and the first precedent snapshot difference list S 21 to recover the first state snapshot S 1 following its deletion; acquiring a third state snapshot S 3 of a third data volume consistent state at a time t 3 >t 2 ; generating a second precedent snapshot difference list S 32 comprising an identification of data blocks of said second state snapshot S 2 differing from data blocks in said third state snapshot S 3 ; and creating a second precedent backup B 32 by copying from said second state snapshot S 2 data blocks identified in said second precedent snapshot difference list S 32 , said second precedent backup B 32 further comprising said second precedent snapshot difference list S 32 .