A recent trend in the IT organizations is the consolidation of server systems using virtualization technologies (e.g. Xen, OpenVZ and VMWare ESX Server) to increase productivity and reduce costs. To reliably operate applications in virtualized machines (VMs), it is important to have Quality of Service (QoS) guarantees, such as minimum amount of allocated CPU and RAM. These virtualization technologies enable VMs to be configured and managed with the aforementioned QoS parameters. However, with respect to application performance, there are still major issues that need to be addressed, such as isolation and response time of running these applications on VMs. This paper examines isolation of VMs in OpenVZ, focusing specifically on I/O intensive workloads. After extensive analysis, several methods that allow a better runtime analysis of resource usage are presented and evaluated.
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