Server Consolidation Techniques in Virtualized Data Centers: A Survey

Data centers and their applications are exponentially growing. Consequently, their energy consumption and environmental impacts have also become increasingly more important. Virtualization technologies are widely used in modern data centers to ease the management of the data center and to reduce its energy consumption. Data centers that employ virtualization technologies are typically called virtualized or cloud data centers. Virtualization technologies enable virtual machine (VM) live migration, which allows the VMs to be freely moved among physical machines (PMs) with negligible downtime. Thus, several VMs can be packed on a single PM so as to let the PM run in its more energy-efficient working condition. This technique is called server consolidation and is an effective and widely used approach to reduce total energy consumption in data centers. Server consolidation can be done in various ways and by considering various parameters and effects. This paper presents a survey and taxonomy for server consolidation techniques in cloud data centers. Special attention has been devoted to the parameters and algorithmic approaches used to consolidate VMs onto PMs. In this end, we also discuss open challenges and suggest areas for further research.