Resource management is the distribution of resources available from resource providers among resource consumers. In the vSphere environment, all resources are shared between resource consumers. Each virtual machine is allocated a certain amount of the host's hardware resources based on a number of factors. With shares, administrators can specify the relative importance of virtual machines or resource pools. A reservation is the minimum guaranteed amount of resources allocated to a virtual machine. Limits are the maximum amount of resources that can be consumed. Resource pools are used for the flexible management of CPU and memory resources. Administrators can group resource pools into hierarchies to partition available resources hierarchically. DRS may be referred to as a joint load-balancing and failover solution. It enables vCenter to manage hosts as an aggregated pool of resources.