Three facts about CPU shares in vSphere

CPU shares are a host level configuration setting that can be applied to virtual machine in vSphere.  Here are three facts about CPU shares that are important for vSphere admins to understand:

• Shares control how many resources a virtual machine is allowed to consume as well as identify some minimum resource allocation for virtual machines that may need it.
• When an administrator makes configuration changes to CPU resource shares, no VM reboot is necessary since the configuration is at the host level and is not a local operating system setting.
• Shares are a proportional resource.  When resources are allocated, it is done on the basis as a percentage of a whole.  If you add resources, all reservations remain the same, but the individual resources are increased.