Quorums
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
use read and write quorums to tune consistency.
Planned topics
- With N replicas, write to W and read from R; if R + W > N, reads overlap the latest write.
- Lower W or R gives speed and availability but weaker guarantees.
- Quorum overlap alone does not give linearizability under failures, concurrent writes, or sloppy quorums.
- Always walk through a failure scenario, not only the arithmetic.
Draft outline details
Demonstration
N=3 examples: W=2,R=2 overlaps; W=1,R=1 may read stale; then a scenario where a node is slow and a hinted handoff leaves a stale read.
Check your understanding
With N=3, W=2, R=2, do reads overlap writes?
Show answer
Yes, since 2 + 2 > 3, subject to caveats under failure.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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