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A Distributed Resource Scheduler (DRS) cluster is displaying a message that recommends the migration of virtual machines, even though the cluster is currently balanced.
What is the likely reason for this?
A. The DRS cluster does not satisfy the resource pool reservations.
B. The DRS cluster is not configured with shared storage.
C. The DRS cluster is in a critical state.
D. The DRS cluster contains hosts with CPU compatibility issues.
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.
Each standalone host and each DRS cluster has an (invisible) root resource pool that groups the resources of that host or cluster. Users can create child resource pools of the root resource pool or of any user-created child resource pool.
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.
In this question, the hosts in the cluster appear to be balanced because the CPU and memory load is similar across all hosts in the cluster. However, DRS looks at the available CPU/Memory on the hosts and compares that to the reservations of the resource pools. If a resource pool has reserved resources that are unavailable on a host, DRS will recommend moving VMs to free up resources on the host to meet the reservation requirements of the resource pools.
Incorrect Answers:
B: Shared storage is a requirement of DRS. The DRS cluster would not be functioning at all (ie. we wouldn’t have a cluster) without shared storage. Therefore, this answer is incorrect.
C: A critical state would indicate a failure of some component of the DRS cluster. In this question, the cluster is balanced but DRS is making recommendations. This indicates the cluster is working as normal and is therefore not in a critical state. Therefore, this answer is incorrect.
D: It is unlikely that the DRS cluster contains hosts with CPU compatibility issues. Enhanced vMotion Compatibility (EVC) is used to enable a cluster to have CPUs with different capabilities (cores, clock speed etc.) If the hosts had incompatible CPUs (for example a mix of Intel and AMD processors), then you would not be able to add the host to the cluster in the first place. Therefore, this answer is incorrect.
References:
https://pubs.vmware.com/vsphere-55/index.jsp#com.vmware.vsphere.resmgmt.doc/GUID-60077B40-66FF-4625-934A-641703ED7601.html