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An application team is implementing a new solution in the virtualized environment. The application vendor states the application is memory intensive.
The application is very unstable when operating without adequate on-demand access to physical memory. The application’s virtual machines are assigned to the Mission Critical resource pool.
Which resource pool setting will help ensure the application has adequate access to memory?
A. Memory reservation
B. High memory share value
C. Unlimited memory
D. Expandable reservation
Correct Answer: A
Explanation/Reference:
Explanation:
A resource pool is a logical grouping of the resources (Memory, CPUs etc.) on an ESXi host or cluster. Resource pools can be grouped into hierarchies and used to hierarchically partition available CPU and memory resources.
When configuring a resource pool, you can configure a “Reservation”. A reservation reserves a defined amount of CPU or memory resource to be used by the resource pool. The reserved resources cannot be used by VMs in another resource pool even if the resources are unused. By configuring a memory reservation in the Mission Critical resource pool, we can ensure that enough memory is available to the application.
Incorrect Answers:
B: Shares in a resource pool assign resources to a VM as a ratio when compared to other VMs. Shares also only come into play when there is resource contention in a resource pool. For example, a VM with a ‘high’ share value will be able to use twice as much memory as a VM with a ‘normal’ share value. A high share value will not guarantee that the application has the memory it needs. Therefore, this answer is incorrect.
C: The limit value is the upper limit for the resource pool’s CPU or memory allocation. An unlimited value for memory in a resource pool means that the resource pool can use an unlimited amount of available memory in the parent resource pool if expandable memory is selected. However, if there is no unused available memory, then it won’t be available to the application. A reservation on the other hand ensures that a defined amount of memory is reserved for the resource pool and is therefore available to the application. Therefore, this answer is incorrect.
D: The expandable reservation setting allows a resource pool to use available resources from its parent resource pool. However, if there is no unused available memory, then it won’t be available to the application. A reservation on the other hand ensures that a defined amount of memory is reserved for the resource pool and is therefore available to the application. Therefore, this answer is incorrect.
References:
http://pubs.vmware.com/vsphere-55/index.jsp#com.vmware.vsphere.resmgmt.doc/GUID-0F6C6709-A5DA-4D38-BE08-6CB1002DD13D.html