Fix the local quorum rule
Fictional read requires at least two of R1/R2/R3. R1 maintenance is 10:00–10:20, R2 is 10:15–10:30, R3 stays available. A replica is unavailable from maintenance start until but not including end. Other failures and write rules are outside scope.
| Segment | Available | Read rule |
|---|---|---|
| 10:00–10:15 | R2,R3 | Pass 2 |
| 10:15–10:20 | R3 | Fail 1 |
| 10:20–10:30 | R1,R3 | Pass 2 |
Split at maintenance endpoints
- Order the endpoints
- Count replicas in each interval
- Mark intervals below two
Do not infer a write quorum from the supplied read rule.
How long is read quorum unavailable?
Show the worked answer
Five minutes,10:15–10:20. At 10:20 R1 is available again; starting R2 at 10:20 instead would avoid overlap under this model.
Count available replicas per segment
| Case | Decision | Reason |
|---|---|---|
| R2 starts 10:15 | 5-minute gap | Only R3 remains |
| R2 starts 10:20 | No overlap gap | R1 returns at boundary |
The alternative is a scheduling candidate. Record confirmed actual maintenance boundaries before claiming no quorum interruption.