Objective 5 – Administer and Manage vSphere 6.x Resources

Objective 5.1: Configure Advanced/Multilevel Resource Pools

  • Determine the effect of the Expandable Reservation parameter on resource allocation
    • When the check box is selected (default), expandable reservations are considered during admission control. If you power on a virtual machine in this resource pool, and the combined reservations of the virtual machines are larger than the reservation of the resource pool, the resource pool can use resources from its parent or ancestors
    • The system considers the resources available in the selected resource pool and its direct parent resource pool. If the parent resource pool also has the Expandable Reservation option selected, it can borrow resources from its parent resource pool. Borrowing resources occurs recursively from the ancestors of the current resource pool as long as the Expandable Reservation option is selected. Leaving this option selected offers more flexibility, but, at the same time provides less protection. A child resource pool owner might reserve more resources than you anticipate.
    • Expandable reservations cause a loss of strict isolation. Sibling1 can start using all of Parents’s reservation, so that no memory or CPU is directly available to Sibling2
  • Create a resource pool hierarchical structure
    • Elements at the same level are siblings. Resources are allocated to siblings based on the parents pool of resources and the relative shares of the siblings
  • Configure custom resource pool attributes
    • The CPU resources for your resource pool are the guaranteed physical resources the host reserves for a resource pool. Normally, you accept the default and let the host handle resource allocation low:normal:high = 1:2:4 ratio
  • Determine how resource pools apply to vApps
    • A vApp is essentially a fancy resource pool.
    • You can create a vapp inside a resource pool or vice versa
  • Create/Remove a Resource Pool
  • Add/Remove virtual machines from a Resource Pool
    • A warning appears if a virtual machine would receive a very large (or very small) percentage of total shares.
    • If a virtual machine is powered on, and the destination resource pool does not have enough CPU or memory to guarantee the virtual machine’s reservation, the move fails because admission control does not allow it.
    • To add or remove, VMware seems to suggest using migrate, but you can drag drop as well
    • When you move a virtual machine to a new resource pool:
      • The virtual machine’s reservation and limit do not change.
      • If the virtual machine’s shares are high, medium, or low, %Shares adjusts to reflect the total number of shares in use in the new resource pool.
      • If the virtual machine has custom shares assigned, the share value is maintained.
  • Given a scenario, determine appropriate shares, reservations and limits for hierarchical Resource Pools