One of the main reasons why cloud computing has gained
so much popularity is due to its ease of use and its ability
to scale computing resources on demand. As a result, users
can now rent computing nodes on large commercial clusters
through several vendors, such as Amazon and rackspace.
However, despite the attention paid by Cloud providers,
performance unpredictability is a major issue in Cloud com-
puting for (1) database researchers performing wall clock ex-
periments, and (2) database applications providing service-
level agreements. In this paper, we carry out a study of the