Physical incremental backup using snapshots

• US 7,197,665 B2
• Filed: 11/03/2003
• Issued: 03/27/2007
• Est. Priority Date: 06/22/2000
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Wrenn, Richard F., Thiel, David W., Goldstein, Andrew C.
• Primary Examiner(s): Baderman; Scott
• Assistant Examiner(s): Bonura; Timothy M
• Application Number:
  US10/700,140
• Publication Number:
  US 20040163009A1
• Time in Patent Office: 1,240 Days
• Field of Search: 714/15, 714/19, 714/20
• US Class Current: 714/20
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data

Abstract

A backup apparatus and method suitable for protecting the data volume in a computer system function by acquiring a base state snapshot and a sequential series of data volume snapshots, the apparatus concurrently generating succedent and precedent lists of snapshot differences which are used to create succedent and precedent backups respectively. The data volume is restored by overwriting the base state data with data blocks identified in one or more succedent backups. File recovery is accomplished by overwriting data from a current snapshot with one or more precedent backups.

Claims

1. A method of protecting computer data, said method comprising the steps of:

acquiring a first state snapshot S1 of a first data volume consistent state at a time t1;

acquiring a second state snapshot S2 of a second data volume consistent state at a time t2>

t1;

generating a first precedent snapshot difference list S21 comprising an identification of data blocks of said first state snapshot S1 differing from data blocks in said second state snapshot S2;

creating a first precedent backup B21 by copying from said first state snapshot S1 data blocks identified in said first precedent snapshot difference list S21, said first precedent backup B21 further comprising said first precedent snapshot difference list S21;

utilizing the first precedent backup B21 and the first precedent snapshot difference list S21 to recover the first state snapshot S1 following its deletion;

acquiring a third state snapshot S3 of a third data volume consistent state at a time t3>

t2;

generating a second precedent snapshot difference list S32 comprising an identification of data blocks of said second state snapshot S2 differing from data blocks in said third state snapshot S3; and

creating a second precedent backup B32 by copying from said second state snapshot S2 data blocks identified in said second precedent snapshot difference list S32, said second precedent backup B32 further comprising said second precedent snapshot difference list S32.

2. The method of claim 1 further comprising the step of utilizing the second precedent backup B₃₂ and the second precedent snapshot difference list S₃₂ to recover the third state snapshot S₃ following its deletion.

3. The method of claim 2 further comprising the steps of:

generating a concatenated precedent snapshot difference list S₃₁ comprising an identification of said data blocks of said second state snapshot S₂ differing from data blocks in said third state snapshot S₃ and an identification of said data blocks of said first state snapshot S₁ differing from data blocks in said second state snapshot S₂;

creating a concatenated backup B₃₁ by copying all said blocks in said first precedent

backup B₂₁ and copying all blocks in said second precedent backup B₃₂ not present in said first precedent backup B₂₁;

copying said first precedent snapshot difference list S₂₁ and said second precedent snapshot difference list S₃₂ into said concatenated backup B₃₁; and

storing said concatenated backup B₃₁ in an offline memory means.

4. The method of claim 3 further comprising the step of utilizing the third state snapshot S₃ and the concatenated backup B₃₁ to recover the first state snapshot S₁ following its deletion.

5. The method of claim 1 further comprising the step of storing said first precedent backup B₂₁ in an offline memory unit.

6. The method of claim 5 wherein said offline memory unit is one of a magnetic-based memory unit and an optical-based memory unit.

7. A method of protecting computer data, said method comprising the steps of:

acquiring a base state snapshot S0 of a base state at a time t0;

acquiring a first state snapshot S1 of a first data volume consistent state at a time t1>

t0;

acquiring a second state snapshot S2 of a second data volume consistent state at a time t2>

t1;

generating a first precedent snapshot difference list S01 comprising an identification of data blocks of said first state snapshot S1 differing from data blocks in said second state snapshot S0;

generating a first precedent snapshot difference list S21 comprising an identification of data blocks of said first state snapshot S1 differing from data blocks in said second state snapshot S2;

creating a first composite backup C012 by copying from said first state snapshot S1 data blocks identified in first succedent snapshot difference list S01 and copying from said first state snapshot S1 data blocks identified in said first precedent snapshot difference list S21;

copying said first succedent snapshot difference list Sol and said first precedent snapshot difference list S21 into said first composite backup C012;

utilizing the second state snapshot S2 and the first composite backup C012 to restore the first state snapshot S1 following its deletion;

acquiring a third state snapshot S3 of a third data volume consistent state at a time t3>

t2;

generating a second succedent snapshot difference list S12 comprising an identification of data blocks of said second state snapshot S2 differing from data blocks in said first state snapshot S1;

generating a second precedent snapshot difference list S32 comprising an identification of data blocks of said second state snapshot S2 differing from data blocks in said third state snapshot S3;

creating a second composite backup C123 by copying from said second state snapshot S2 data blocks identified in second succedent snapshot difference list S12 and copying from said second state snapshot S2 data blocks identified in said second precedent snapshot difference list S32; and

copying said second succedent snapshot difference list S12 and said second precedent snapshot difference list S32 into said second composite backup C123.

8. The method of claim 7 further comprising the steps of:

acquiring a plurality of third through n^th state snapshots S₃ through S_n of third through n^th data volume consistent states at respective times t₃<

. . . t_j . . . ≦

t_n;

generating second through (n−

1)^th succedent snapshot difference lists S₁₂ through S<sub>(n−

2)(n−

1)</sub> respectively, a (j−

1)^th succedent snapshot difference list S<sub>(j−

2)(j−

1)</sub> comprising an identification of data blocks of a (j−

1)^th state snapshot S<sub>(j−

1)</sub> differing from data blocks in a (j−

2)^th state snapshot S<sub>(j−

2)</sub>;

generating second through (n−

1)^th precedent snapshot difference lists S₃₂ through S<sub>(n)(n−

1)</sub> respectively, a (j−

1)^th precedent snapshot difference list S<sub>(j)(j−

1)</sub> comprising an identification of data blocks of a (j−

1)^th state snapshot S<sub>(j−

1)</sub> differing from data blocks in a j^th state snapshot S_j;

creating second through (n−

1)^th composite backups C₁₂₃ through C<sub>(n−

2)(n−

1)(n)</sub>, wherein a (j−

1)^th composite backup C<sub>(j−

2)(j−

1)(j)</sub> is created by copying from said (j−

1)^th state snapshot S<sub>(j−

1)</sub> data blocks identified in said (j−

1)^th succedent snapshot difference list S<sub>(j−

2)(j−

1)</sub> and copying from said (j−

1)^th state snapshot S<sub>(j−

1)</sub> data blocks identified in said (j−

1)^th precedent snapshot difference list S<sub>(j)(j−

1)</sub>; and

copying said succedent snapshot difference lists S₁₂ through S<sub>(n−

2)(n−

1)</sub> and said precedent snapshot difference lists S₃₂ through S<sub>(n)(n−

1)</sub> into said respective composite backups C₁₂₃ through C<sub>(n−

2)(n−

1)(n)</sub>.

9. The method of claim 8 further comprising the steps of:

assigning a unique identifier to each said state snapshot S_j;

for each said composite backup C<sub>(j−

2)(j−

1)(j)</sub>, identifying said state snapshots S<sub>(j−

2)</sub> and S_j as difference snapshots and said (j−

1)^th state snapshot S<sub>(j−

1)</sub> as a content snapshot;

for each said composite backup C<sub>(j−

2)(j−

1)(j)</sub>, copying the unique identifiers of said state snapshots S<sub>(j−

2)</sub>, S<sub>(j−

1)</sub>, and S_j into said (j−

1)^th composite backup C<sub>(j−

2)(j−

1)(j)</sub>.

10. The method of claim 9 further comprising the step of comparing the unique identifier of said j^th snapshot S_j to the unique identifiers of the difference snapshots of said (j−

1)^th composite backup C<sub>(j−

2)(j−

1)(j)</sub>.