Date Added: Aug 2012
In this paper, the authors present the design, implementation, and evaluation of a pluggable autoscaler within an open cloud Platform-as-a-Service (PaaS). They redefine High Availability (HA) as the dynamic use of virtual machines to keep services available to users, making it a subset of elasticity (the dynamic use of virtual machines). This makes it possible to investigate autoscalers that simultaneously address HA and elasticity. They present and evaluate autoscalers within this pluggable system that are HA-aware and Quality-of-Service (QoS)-aware for web applications written in different programming languages. Hot spares can also be utilized to provide both HA and improve QoS to web users.