| SR | Sequential Rotation |
|---|
|
| Mon | Tue | Wed | Thu | Fri |
|---|
| Tape | 1 | 2 | 3 | 4 | 1 |
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|
| Example: Four tapes |
| Backup daily. |
| When reach tape N start again at tape 1 |
| Takes N tapes |
| Recovery window: 4 days (based on total number of tapes) |
| | |
| FS | Father-Son |
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|
| Mon | Tue | Wed | Thu | Fri |
|---|
| Tape | A | B | C | D | Friday 1 |
|---|
| | | | | Friday 2 |
| | | | | Friday 3 |
| | | | | Friday 1 |
|
| Example: Four daily tapes, three Friday tapes |
| 4 Tapes - M-Th |
| |
| N tapes for Friday |
| - Perform sequential rotation on the Friday tapes
|
| Takes 4 +N tapes (depending on how many Friday tapes you want) |
| Daily tapes see more wear |
| Recovery window: 3 weeks (based on Firday tapes) |
| | |
| GFS | GrandFather-Father-Son |
|---|
| 4 Tapes - M-Th |
| |
| 3 tapes for Friday(1-3) |
| - Perform sequential rotation on the Friday tapes
|
| 3 tapes for Monthly(1-3) |
| - when 3th Friday tape is used use next monthly tape
|
| - Perform sequential rotation on monthly tapes
|
| Cycle repeats every 4 months |
| Note: no distinction for longer/shorter months than others |
| Takes 10 tapes |
| Daily tapes see most wear |
| Recovery window: 3 months (based on monthly tapes) | |
| | |
| GGFS | GreatGrandfather-GrandFather-Father-Son |
|---|
| 4 tapes - M-Th |
| |
| 3 tapes for Friday(1-3) |
| - Perform sequential rotation on the Friday tapes
|
| 3 tapes for Monthly(1-3) |
| - when 3th Friday tape is used use next monthly tape
|
| - Perform sequential rotation on monthly tapes
|
| 3 tapes for Quarterly(1-3) - optional |
| - Backup on last Friday of March, June, Sept is Quarter 1,2,3 respectivly
|
| 3 tapes for Yearly(1-3) |
| - Last Friday tape of the year is the yearly tape
|
| - Perform sequential rotation on yearly tapes
|
| Cycle repeats every 3 years |
| Note: no distinction for longer/shorter months than others |
| Needs 13-16 tapes |
| Requires the most number of tapes |
| Daily tapes see excessive wear |
| Recovery window: 3 Years (based on total number of yearly tapes) |
| | |
| IR | Incremental-Rotation |
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|
| Mon | Tue | Wed | Thu | Fri |
|---|
| Week 1 | 1 | 2 | 3 | 4 | 5 |
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| Week 2 | 2 | 3 | 4 | 5 | 6 |
|---|
| Week 3 | 3 | 4 | 5 | 6 | 7 |
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| Week 4 | 4 | 5 | 6 | 7 | 8 |
|---|
| Week 5 | 5 | 6 | 7 | 8 | 9 |
|---|
| Week 6 | 6 | 7 | 8 | 9 | 1 |
|---|
| Week 7 | 7 | 8 | 9 | 1 | 2 |
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|
| Tapes are numbered 1-N - example is 9 |
| To extend add more tapes at end |
| Even usage and wear to all tapes |
| Take N tapes |
| Each tape adds another week of backup |
| Recovery window: 5 weeks (N-4) - (based on number of tapes) |
| | |
| TOH | Tower of Hanoi
|
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|
| A | A | | A | | A | | A | | A | | A | | A | | A |
|---|
| B | | B | | | | B | | | | B | | | | B | |
|---|
| C | | | | C | | | | | | | | C | | | |
|---|
| D | | | | | | | | D | | | | | | | |
|---|
|
| Example: Four tapes A-D |
| Minimum number of tapes (N) |
| Each extra tape doubles the days covered |
| Most complex of all backup schemes |
| 'A' tape used 2 X more than 'B' tape etc. |
| Tapes (A) see extreme wear |
| Recovery window: 2^N or 8 days (based on number of tapes) |