Definition - What does VM Rightsizing mean?
VM rightsizing is an administrative process wherein system administrators optimize the allocation of resources within a virtualized hardware environment.
Techopedia explains VM Rightsizing
In general, virtual systems are set up to be as efficient as possible. However, common problems with the operation of virtual systems arise over time. Individual virtual machines (VMs) are supposed to have the right levels of processing power, memory and disk space. Sometimes, though, they do not use what has been allocated to them, which results in inefficiency.
In VM rightsizing, system administrators assess the virtual CPU processing power allocated to a VM. They also look at the assigned RAM and virtual disk space, and what the VM uses.
Although administrators can use manual VM rightsizing, there are software tools available that provide this kind of administration. These tools can either suggest manual pre-provisioning of resources or, in some cases, change the provisioning automatically. All of these strategies are subject to hardware and software requirements, and must work with administrative schedulers and other software tools that support ongoing operations.