350 Large Scale and Big Data
a higher level of consistency is larger). Network latency is high and varies in time
in Amazon EC2 (we observe it is 5 times higher than in a local cluster). We run
workload-A while varying the number of client threads.
Figure 10.4a presents the 99th percentile latency of read operations when the
number of client threads increases on EC2. The strong consistency approach pro-
vides the highest latency having all reads to wait for responses from all repli-
cas that are spread over different racks and clusters. Eventual consistency is the
approach that provides the smallest latencies since all read operations are per-
formed on one local replica (possibly at the cost of consistency violation). We can
clearly see that Ha ...