  Users of cloud computing are overwhelmed with choice, even within the
services offered by one provider. As such, many users select cloud services
based on description alone. We investigate the degree to which such strategy is
optimal. In this quantitative study, we investigate the services of 2 of major
IaaS providers. We use 2 representative applications to obtain longitudinal
observations over 7 days of the week and over different times of the day,
totalling over 14,000 executions. We give evidence of significant variations of
performance offered within IaaS services, calling for brokers to use automated
and adaptive decision making processes with means for incorporating expressive
user constraints.
