Assume a parent resource pool RP-MOM has a reservation of 6GHz and one running virtual machine VM-M1 that reserves 1GHz. RP-MOM also has a child resource pool RP-KID with a reservation of 2GHz and with Expandable Reservation selected. RP-KID contains two virtual machines, VM-K1 and VM-K2, with reservations of 2GHz each.
When a user powers on VM-K1, it can reserve the resources it needs directly from RP-KID (which has 2GHz). When the user tries to power on VM-K2, RP-KID has already allocated its 2GHz reservation to VM-K1, but it has Expandable Reservation configured, so it tries to borrow resources from RP-MOM's reservation. RP-MOM has 6GHz minus 1GHz (reserved by VM-M1) minus 2GHz (reserved by RP-KID), which leaves 3GHz of RP-MOM's reservation that is not reserved by other resource pools or virtual machines in RP-MOM. With 3GHz available, VM-K2 is able to power on.
