DRIVE - Dispatching Requests Indirectly through Virtual Environment

Abstract

Dispatching a large number of dynamically changing requests directly to a small number of servers exposes the disparity between the requests and the machines. In this paper, we present a novel approach that dispatches requests to servers through virtual machines, called Dispatching Requests Indirectly through Virtual Environment (DRIVE). Client requests are first dispatched to virtual machines that are subsequently dispatched to actual physical machines. This buffering of requests helps to reduce the complexity involved in dispatching a large number of requests to a small number of machines. To demonstrate the effectiveness of the DRIVE framework, we set up an experimental environment consisting of a PC cluster and four benchmark suites. With the experimental results, we demonstrate that the use of virtual machines indeed abstracts away the client requests and hence helps to improve the overall performance of a dynamically changing computing environment. DISPATCHING REQUESTS INDIRECTLY THROUGH VIRTUAL ENVIRONMENT399 relatively small number of backend servers. By placing a dispatcher at the entry to the infrastructure, the incoming requests can be quickly distributed to the computing resources in such a way that each server handles requests reasonably equally at any point in time. However, this 'reasonably equal' distribution is rather difficult to achieve since it involves various parameters such as job arrival rate, job distribution time, server status, processing time, etc.[1].Popular web sites dynamically assign and distribute a large number of client requests to the proper servers to balance the loads. One of the techniques involves packet rewriting, which is eventually delivering to the target servers [2,3]. The load unbalancing approach [4] to balance the loads across a cluster is based on the observation that using the correlation between the arrival rate and the processing rate is not necessarily a good approach; hence, resulting in uncorrelating the two. A hierarchical controller framework in [5] uses three levels of controllers to effectively manage the power consumed by a cluster, where forecast and operating environment parameters are used to manage the interactions between multilevels. While the dispatcher-based approach relays client requests directly to physical machines, server virtualization [6] offers an indirect buffering mechanism that abstracts away the underlying physical machines for workload management.Virtualization enables multiple virtual machines to run on a physical machine or host operating system [6]. Commercial virtualization techniques and products include EMC's VMware [7], Microsoft's Virtual Server [8], etc. Open-source and academic virtualization techniques include Xen and its hypervisor [9], User Mode Linux (UML) [10], Bochs [11], QEMU [12], etc. Hardware support for virtualization comes from Intel's Virtualization Technology [13] and AMD's AMD-V [14]. These virtualization technologies provide various means to abstract the resources and hence enable the users to have an illusi...