Virtualization Oversubscription - What’s so scary? Reservations, Shares and Limits (15 of 20)

Reservations, Shares and Limits apply to the amount of CPU and Memory a VM or Resource pool can use.
In the example below we have an Engineering Resource Pool containing 2 Virtual Machines.

Test has 1000  CPU shares and Production has 2000 CPU shares, giving a total of 3000 shares between them.  If there is contention for CPU resource then Production will be given twice as much CPU time as Test.

Also notice the reservation on the Resource Pool has an Expandable Reservation.  This means that if there is another resource pool not using its reservation Engineering could claim and use that reservation if required.  This could cause problems if the 2^nd resource pool wishes to use its reservation as it will not be able to push Engineering out.  So while this may provide flexibility its use should be closely monitored.

On Wednesday I'll give a quick demonstration of what a reservation does.

Phil Bell

Consultant