VCP-DCV vSphere Performance and Scaling Practice Test 6 — 15 Questions

Question 1

An administrator is troubleshooting a vSphere cluster where several VMs experience intermittent performance degradation. The esxtop output shows high CPU ready time and high memory ballooning. Which TWO actions should the administrator take to improve performance? (Choose two.)

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Reduce the number of vCPUs assigned to the affected VMs.. High CPU ready time is often caused by overprovisioned vCPUs, so reducing vCPU count can improve scheduling. High ballooning indicates memory pressure, and increasing memory reservations ensures the VM's memory is not reclaimed. Together, these actions address both symptoms effectively.

Answer

Add more physical memory to the host.

Answer

Migrate the affected VMs to a host with more available CPU and memory resources.

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Enable CPU affinity for the affected VMs to pin them to specific cores.

Question 2

A vSphere administrator manages a cluster where several production VMs run latency-sensitive trading applications. The administrator notices that these VMs occasionally experience high CPU ready time. The host has ample physical cores, and no CPU overcommitment is present. The administrator wants to ensure that these VMs are prioritized for CPU scheduling and can preempt other VMs when needed. Which action should the administrator take?

Accepted Answer

Enable CPU latency sensitivity on the latency-sensitive VMs by setting the latency sensitivity flag to high.. For latency-sensitive workloads, vSphere provides a latency sensitivity setting that, when set to high, allows the VM to preempt other VMs and receive CPU resources with minimal delay. This is the correct approach because it directly addresses scheduling delays without relying on shares or reservations, which are ineffective when there is no CPU contention.

Answer

Set a CPU reservation on each latency-sensitive VM equal to its configured vCPU count.

Answer

Create a resource pool with a high CPU shares value and place the latency-sensitive VMs in it.

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Configure CPU affinity for the latency-sensitive VMs to specific physical cores.

Question 3

A vSphere administrator needs to ensure that a latency-sensitive trading application VM receives dedicated CPU resources and is not affected by other VMs on the host. The host has 16 physical cores and runs 10 other VMs. Which vSphere feature should the administrator configure?

Accepted Answer

CPU reservation. A CPU reservation guarantees a specific amount of CPU resources for the VM, ensuring it has dedicated access to physical cores even when the host is contended. This meets the requirement for a latency-sensitive application that needs consistent performance.

Answer

CPU affinity

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CPU shares

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CPU limit

Question 4

A vSphere administrator is troubleshooting performance issues in a cluster where multiple VMs experience high CPU ready time. The host has 24 logical processors and is running 30 VMs, each with 2 vCPUs. The administrator wants to reduce CPU ready time without adding more hosts. Which two actions should the administrator take? (Choose two.)

Accepted Answer

Enable hyperthreading on the host if it is not already enabled.. Right-sizing VMs by reducing unnecessary vCPUs lowers the total scheduling demand, and enabling hyperthreading increases the number of logical processors available for scheduling. Both actions directly reduce CPU ready time by improving the ratio of vCPUs to physical cores and enhancing scheduling efficiency, without requiring additional hosts.

Answer

Set a CPU limit on all VMs to prevent them from using more than their fair share.

Answer

Increase the CPU shares value for all VMs in the cluster.

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Migrate some VMs to another host using vMotion.

Question 5

A vSphere administrator is configuring Network I/O Control (NIOC) on a vSphere Distributed Switch to prioritize storage traffic. The environment uses iSCSI storage and has separate VMkernel adapters for iSCSI and vMotion. Which action ensures that iSCSI traffic receives guaranteed bandwidth during congestion?

Accepted Answer

Assign a reservation to the iSCSI VMkernel adapter's network resource pool.. NIOC reservations guarantee a minimum amount of bandwidth for a network resource pool. By assigning a reservation to the iSCSI traffic's resource pool, the administrator ensures that iSCSI traffic receives its guaranteed bandwidth even when the physical uplink is congested.

Answer

Set the iSCSI VMkernel adapter to use a dedicated physical uplink.

Answer

Enable jumbo frames on the iSCSI VMkernel adapter.

Answer

Create a network resource pool for iSCSI traffic and assign a high share value.

Question 6

A vSphere administrator observes that a VM's memory usage is consistently at 95% of its configured 8 GB, and the host's memory is overcommitted. The VM's guest OS reports high swap usage. Which action should the administrator take to improve the VM's performance while minimizing host memory pressure?

Accepted Answer

Increase the VM's configured memory to 12 GB.. The VM's guest OS is swapping because it lacks sufficient memory. Increasing the configured memory gives the guest more RAM to work with, reducing swap usage and improving performance. While this increases host memory pressure, it is the correct first step; the administrator should then assess host capacity.

Answer

Set a memory limit of 8 GB on the VM.

Answer

Increase the VM's memory reservation to 8 GB.

Answer

Enable memory ballooning for the VM.

Question 7

A company's vSphere environment has multiple clusters with varying workloads. The operations team notices that one cluster consistently shows high CPU ready times on several hosts. Which action should be taken to address this performance issue?

Accepted Answer

Reduce the number of virtual CPUs assigned to VMs and consider adding more hosts.. High CPU ready times indicate that VMs are contending for physical CPU resources because the host is over-provisioned with vCPUs relative to available pCPUs. Reducing the number of vCPUs per VM decreases scheduling overhead and contention, while adding more hosts increases the total pCPU count, directly alleviating the bottleneck. Option C correctly addresses both the demand-side (vCPU reduction) and supply-side (host addition) of the CPU scheduling issue.

Answer

Increase the memory allocation of VMs with high CPU ready times.

Answer

Increase the CPU reservation for VMs with high ready times.

Answer

Enable Storage DRS to balance storage I/O load.

Question 8

A vSphere administrator is troubleshooting a VM that is experiencing excessive disk latency. The VM is on a datastore accessed via NFS over a 1GbE network. The host shows high network utilization. Which action should be taken to improve performance?

Accepted Answer

Upgrade the network link to 10GbE or enable multiple NICs with teaming.. The VM is experiencing excessive disk latency due to high network utilization on the 1GbE link. Since NFS storage traffic is entirely network-bound, upgrading to 10GbE or enabling multiple NICs with teaming increases the available bandwidth, reduces congestion, and directly addresses the root cause of the latency. This is the most effective action because the bottleneck is at the network layer, not the storage protocol or VM configuration.

Answer

Enable Storage I/O Control on the datastore.

Answer

Convert the datastore from NFS to VMFS.

Answer

Increase the memory reservation for the VM.

Question 9

Refer to the exhibit. The performance data shows MEMCTL at 5% and SWPOUT at 2%. What does this indicate about the host?

Accepted Answer

The host is over-committed on memory, causing ballooning and swapping.. MEMCTL at 5% indicates the ESXi host's memory balloon driver (vmmemctl) is actively reclaiming memory from virtual machines, while SWPOUT at 2% shows the host is swapping guest memory to disk. Together, these values confirm the host is over-committed on memory, forcing the hypervisor to use both ballooning and swapping to free up memory for VMs.

Answer

The host is experiencing CPU contention.

Answer

The host has network congestion.

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The host has high storage latency.

Question 10

Refer to the exhibit. A distributed virtual switch port shows dropped Rx packets and CRC errors. What is the most likely cause?

Accepted Answer

Faulty physical network cable or NIC.. CRC errors and dropped Rx packets on a distributed virtual switch port indicate physical-layer corruption of frames, typically caused by a faulty cable, damaged NIC, or bad transceiver. These errors occur when the cyclic redundancy check (CRC) computed by the receiver does not match the frame's CRC field, which is a direct symptom of signal integrity issues at Layer 1.

Answer

Outdated NIC driver on the ESXi host.

Answer

MTU mismatch between the switch and the VM.

Answer

Incorrect VLAN configuration on the port group.

Question 11

An administrator notices that a critical VM running a database has a high CPU ready time average (over 20%) on a host with 2 physical CPUs (16 cores each). The host is running 6 VMs, each with 8 vCPUs. What is the most likely cause of the high ready time?

Accepted Answer

The host has too many vCPUs relative to physical cores; reduce vCPU count on some VMs.. The host has 32 physical cores (2 CPUs × 16 cores) but the 6 VMs each with 8 vCPUs total 48 vCPUs, resulting in a vCPU-to-core ratio of 1.5:1. A CPU ready time average over 20% indicates severe contention for physical cores, as the hypervisor cannot schedule all vCPUs simultaneously. Reducing the vCPU count on some VMs would lower the ratio and alleviate the scheduling bottleneck.

Answer

Hyper-Threading should be disabled to reduce scheduling overhead.

Answer

The VMs are not configured with NUMA awareness.

Answer

Memory overcommitment is causing excessive swapping.

Question 12

An administrator is troubleshooting a VM that is running slowly. The VM has 4 vCPUs and 16 GB of memory. The host has 2 physical CPUs with 10 cores each, hyper-threading enabled. The administrator runs esxtop and sees that %RDY for the VM is consistently above 15%. Which action would most likely reduce the ready time?

Accepted Answer

Reduce the number of vCPUs to 2 if the workload does not require 4.. A %RDY value consistently above 15% indicates the VM is ready to run but is waiting for CPU scheduling time on the host. With 4 vCPUs on a host that has 20 logical CPUs (2 sockets × 10 cores × 2 threads), the VM is likely over-provisioned relative to its workload needs, causing co-scheduling contention. Reducing the number of vCPUs to 2 decreases the co-scheduling demands and reduces ready time, as the VM will require fewer physical CPUs to be available simultaneously. Therefore, option D is correct. Increasing CPU shares (option A) would not help if the host is saturated, adding more vCPUs (option B) would worsen contention, and increasing memory (option C) does not address CPU ready time.

Answer

Increase the CPU shares for the VM.

Answer

Increase the number of vCPUs to 8 to improve parallelism.

Answer

Increase the memory allocation to 32 GB.

Question 13

Which TWO actions can help reduce network latency for a latency-sensitive VM in a vSphere environment? (Choose two.)

Accepted Answer

Configure NetQueue on the physical NIC.. Option B is correct because NetQueue allows the physical NIC to use multiple receive queues and distribute network traffic across multiple CPUs, reducing per-packet processing latency and improving throughput for latency-sensitive workloads. Option C is correct because SR-IOV lets the VM bypass the virtual switch datapath by directly accessing a virtual function on the physical NIC, which significantly lowers latency and CPU overhead. Option A is incorrect because a standard vSwitch versus a distributed switch does not inherently reduce network latency; both are software-based datapaths. Option D is incorrect because jumbo frames reduce per-packet overhead and CPU utilization but do not directly lower latency, and they require end-to-end MTU consistency. Option E is incorrect because disabling TCP segmentation offload increases CPU overhead and can degrade, not improve, network performance.

Answer

Use a standard virtual switch instead of a distributed switch.

Answer

Enable jumbo frames on the virtual switch.

Answer

Disable TCP segmentation offload on the VM.

Question 14

Which THREE factors should be considered when sizing a host cluster for a VDI environment with 1000 desktops? (Choose three.)

Accepted Answer

Storage IOPS capacity for boot storms.. Option C is correct because boot storms in a 1000-desktop VDI environment generate massive concurrent storage I/O, so the datastore's IOPS capacity (and latency) must be sized to absorb peak demand without degrading performance. Option D is correct because VDI workloads are CPU-intensive, so the vCPU-to-physical-core ratio must be kept within acceptable limits (typically 4:1 to 8:1 depending on workload) to prevent CPU contention and ready time. Option E is correct because memory is usually the most constrained resource in VDI; the memory overcommitment ratio and per-host available memory must be calculated so that each desktop receives its required working set without excessive swapping or ballooning. Option A is not a sizing factor but a design/operational requirement for cluster mobility, and Option B, while relevant to performance tuning, is not a primary capacity-sizing factor for the cluster.

Answer

vMotion compatibility between hosts.

Answer

NUMA alignment of virtual desktops.

Question 15

An administrator is troubleshooting performance issues on a vSphere cluster. Which TWO metrics should be monitored to identify CPU ready time contention?

Accepted Answer

Co-Stop. CPU ready time contention occurs when a virtual machine is ready to execute instructions but the ESXi host's CPU scheduler cannot immediately allocate physical CPU cycles. The %RDY metric directly measures the percentage of time a VM is waiting to be scheduled on a physical CPU, while Co-Stop specifically tracks time lost when vCPUs in a single VM are forcibly co-scheduled and then descheduled due to contention on the same physical core. Both metrics are primary indicators of CPU scheduling pressure.

Answer

Disk Kernel Latency

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Memory Swap In Rate

Answer

Network Packet Drop Rate