Systems management involves the supervision and management of information technology resources in an enterprise (or other organization). For example, systems management software may include tools for monitoring and collecting information regarding resource usage. As enterprises grow, their needs for information technology resources can change rapidly. These changing needs are often due, in part, to increasing demands for performance and reliability from their information technology resources. One approach for addressing such growing demands is to consolidate information technology hardware in order to maximize available resources. For example, numerous applications can be consolidated on a reduced number of high performance servers or on a single high performance server running multiple virtual machines.
A virtual machine is typically a logical entity that is implemented over a hardware platform and operating system and can use multiple resources (such as memory, processors, network systems, etc.) to create virtual systems, each of which can run independently as a copy of the operating system. In other words, a virtual machine can be thought of as a computer that operates inside one or more hardware systems, such as a server. Each virtual machine can operate independently of other virtual machines and yet utilize the same hardware resources. Virtual machines can provide flexibility across platforms and can provide performance optimization by allowing efficient hardware to be shared to average out resource demands and benefit from economies of scale.
Virtual machine software, such as VMWARE ESX SERVER (“ESX”), can be used to consolidate systems in advanced environments. Such systems may include individual computers, servers, networks, and other computing resources. For example, ESX can provide a virtualization software tool that deploys multiple, secure, isolated virtual machines, with respective allocated memory shares and/or processor shares, on a single system where a user can specify system resource allocations for any virtual machine as needed. However, if system resources are over-allocated, under-utilization of system resources can be expected. On the other hand, under-allocating resources, which may result in scarcity, is also problematic.