Principles Of Distributed Database Systems Exercise Solutions Guide

Ensuring atomicity (all nodes commit or all nodes abort) is critical.

You have a replicated data item across 5 sites (S1..S5). A quorum consensus protocol requires R readers and W writers, with R+W > N. Given failures or network partitions, determine if reads/writes succeed.

Problem:

Compare the cost of:

Solution:

Strategy 1: Move R to Site 2

Strategy 2: Move S to Site 1

Strategy 3: Semi-Join (Reduce R before moving) Step 1: Send join column of $S$ to Site 1.

Step 2: Reduce $R$ at Site 1.

Step 3: Send $R'$ to Site 2 (if result needed there) or proceed. Ensuring atomicity (all nodes commit or all nodes

Comparison:

Exercises on deadlock detection typically provide a global wait-for graph or local graphs per site.

In distributed systems, the cost model is dominated by network communication cost (transfer of data between sites). The goal is to minimize data transfer volume. Compare the cost of: