VCP-DCV vSphere Performance and Scaling Practice Test 5 — 15 Questions

Question 1

A VMware vSphere cluster uses vSphere Fault Tolerance (FT) for a critical virtual machine with 4 vCPUs. The administrator notices increased latency and CPU ready time on the primary VM. What is the most likely cause?

Accepted Answer

The VM has more than 2 vCPUs, increasing the overhead of deterministic replay.. Option C is correct because vSphere FT for multi-vCPU VMs uses a deterministic record/replay mechanism that can introduce significant overhead, especially with 4 vCPUs. Option A is incorrect because jumbo frames are not a main cause of FT overhead. Option B is incorrect because FT does not use multicast. Option D is incorrect because thin provisioning does not directly affect CPU performance.

Answer

The network between the primary and secondary VM uses jumbo frames.

Answer

The virtual disks are thinly provisioned, causing I/O latency.

Answer

The FT logging traffic is sent over multicast, causing packet loss.

Question 2

An administrator configures a resource pool with a CPU reservation and expandable reservation enabled. The root resource pool has 100% of cluster CPU resources. A VM inside the resource pool with no reservation requests CPU resources. What will happen when the VM tries to power on?

Accepted Answer

The VM can power on using resources from the resource pool or its parent due to expandable reservation.. Option D is correct because expandable reservation allows the resource pool to borrow CPU resources from the parent pool if needed. Since the VM has no reservation, it can power on as long as there are any unreserved resources in the resource pool or parent. Option A is incorrect because the VM can power on without a reservation. Option B is incorrect because reservation is not mandatory to power on. Option C is incorrect because expandable reservation allows borrowing from parent.

Answer

The VM can power on but will be limited to the resource pool's shares.

Answer

The VM cannot power on because the resource pool has a reservation set.

Answer

The VM can power on using resources from the resource pool only if it has a reservation.

Question 3

An administrator is planning a vMotion migration and wants to minimize the performance impact on the virtual machines during the migration. Which network configuration is recommended?

Accepted Answer

Create a dedicated VMkernel interface with at least 10 GbE throughput for vMotion.. Option D is correct because a dedicated VMkernel interface for vMotion ensures that migration traffic does not compete with other types of traffic, reducing latency and improving throughput. Option A is incorrect because using the management network can cause contention. Option B is incorrect because large send offload is not a substitute for dedicated interface. Option C is incorrect because 1 GbE may be insufficient for large VMs.

Answer

Use the default management VMkernel interface for vMotion traffic.

Answer

Configure a single 1 GbE interface for both vMotion and management traffic.

Answer

Enable jumbo frames on all interfaces, but keep vMotion on the management network.

Question 4

An ESXi host experiences high memory ballooning in virtual machines. The administrator checks the host's memory metrics and sees a high swap rate. The host has 512 GB of memory, and the VMs are configured with memory reservations. Which configuration is most likely contributing to the excessive swapping?

Accepted Answer

Memory overcommitment is high, and some VMs have large memory reservations.. Option C is correct because when memory is overcommitted and VMs have reservations but the host is under memory pressure, the hypervisor may still swap to free up memory for reservations. Option A is incorrect because TPS is typically beneficial and does not cause swapping. Option B is incorrect because NUMA interleaving does not cause memory pressure. Option D is incorrect because memory shares do not affect ballooning; they affect proportional distribution.

Answer

Memory shares are set too low for the VMs experiencing ballooning.

Answer

The host is configured for NUMA interleaving, causing memory access delays.

Answer

Transparent Page Sharing (TPS) is enabled and is aggressively sharing memory pages.

Question 5

A vSphere cluster has 10 ESXi hosts configured with vSphere DRS. The administrator wants to ensure that a group of VMs running a latency-sensitive application are always placed on the same host. Which DRS rule should be created?

Accepted Answer

VM-VM affinity rule with a 'must run on the same host' constraint.. Option B is correct because a VM-VM affinity rule (Must run on the same host) ensures that VMs in a group are kept together. Option A is incorrect because host affinity rules affect VM-host relationships, not VM-VM. Option C is incorrect because should run on hosts is a preference, not mandatory. Option D is incorrect because Separate VMs rule does the opposite.

Answer

VM-to-Host affinity rule with a 'should run on hosts in group' constraint.

Answer

VM-VM affinity rule with a 'should run on the same host' constraint.

Answer

VM-VM anti-affinity rule with a 'separate VMs' constraint.

Question 6

What is the maximum number of virtual CPUs (vCPUs) that can be allocated to a virtual machine on vSphere 8 Enterprise Plus?

Accepted Answer

256. Option A is correct because vSphere 8 supports up to 256 vCPUs per VM (with appropriate licensing). Option B is incorrect because 128 was the limit in vSphere 6.5. Option C is incorrect because 512 is not supported. Option D is incorrect because 64 is lower than current maximum.

Answer

128

Answer

512

Answer

64

Question 7

An administrator is troubleshooting a virtual machine that experiences intermittent performance issues. The VM is configured with 8 vCPUs and 32 GB memory. The administrator runs esxtop and sees that the %RDY for the VM is consistently above 20%. What does this indicate?

Accepted Answer

The VM is contending for CPU resources due to overallocation of vCPUs.. Option D is correct because high %RDY means the VM is ready to run but is waiting for CPU resources from the hypervisor; this indicates CPU overcommitment. Option A is incorrect because high %RDY does not directly correlate with memory. Option C is incorrect because storage latency is not shown in CPU %RDY. Option B is incorrect because high %RDY is a sign of CPU contention, not just normal utilization.

Answer

The VM's virtual disks are experiencing high latency.

Answer

The VM is experiencing memory ballooning.

Answer

The VM is using its CPU resources efficiently.

Question 8

Which TWO conditions must be met for a successful Storage vMotion of a virtual machine with a raw device mapping (RDM) in physical compatibility mode?

Accepted Answer

The source and target datastores support SCSI-3 persistent reservations.. Option A is correct because the source and target datastores must support SCSI-3 persistent reservations. Option D is correct because the destination datastore must be compatible with physical RDMs. Option B is incorrect because RDM vMotion does not require shared storage. Option C is incorrect because the VM can be powered on. Option E is incorrect because RDM vMotion does not require the same storage array.

Answer

The source and target are on the same storage array.

Answer

The virtual machine is using a shared virtual SCSI controller.

Answer

The virtual machine must be powered off.

Question 9

Which THREE factors should be considered when designing a vSphere environment to minimize vCPU overcommitment and improve performance for CPU-intensive workloads?

Accepted Answer

Align VM memory with NUMA nodes to reduce remote memory access.. Option B is correct because more physical cores reduce contention. Option C is correct because vSphere can use core-level scheduling to improve performance. Option D is correct because NUMA awareness ensures VMs are scheduled on local memory. Option A is incorrect because large vCPUs can increase overhead. Option E is incorrect because simultaneous multithreading (hyperthreading) increases logical CPUs but may not reduce overcommitment for heavily CPU-bound workloads.

Answer

Use VMs with a high number of vCPUs (e.g., 2:1 ratio to pCPUs).

Answer

Enable Hyper-Threading on all hosts.

Question 10

Which TWO actions are valid for optimizing network performance for vSphere clusters configured with Network I/O Control (NIOC)?

Accepted Answer

Allocate network shares to different traffic types based on business priority.. Option A is correct because shares allocation manages bandwidth proportionally. Option D is correct because reserving bandwidth guarantees minimum throughput. Option B is incorrect because disabling NIOC reduces control. Option C is incorrect because NIOC is typically used at the host level, not across clusters with host profiles alone. Option E is incorrect because traffic shaping is for individual VMs, not NIOC.

Answer

Enable traffic shaping on every virtual machine.

Answer

Disable NIOC on the virtual switch to reduce overhead.

Answer

Use host profiles to apply the same NIOC settings to all hosts in the cluster.

Question 11

A VM is experiencing high CPU ready time. The host has 16 physical cores and 20 vCPUs total across all VMs. Which action is MOST likely to reduce the CPU ready time on the VM?

Accepted Answer

Decrease the number of vCPUs on the VM.. Reducing the number of vCPUs on an over-provisioned VM decreases scheduling contention, lowering CPU ready time. Increasing vCPUs would worsen the issue. Migrating to another host with similar load would not help long-term. Increasing memory does not directly reduce CPU contention.

Answer

Migrate the VM to another host with the same CPU load.

Answer

Increase the number of vCPUs on the VM.

Answer

Increase the memory reservation for the VM.

Question 12

A large VM with 24 vCPUs is deployed on a dual-socket host with two NUMA nodes each having 12 cores. Which step is a BEST PRACTICE to ensure optimal performance for this VM?

Accepted Answer

Leave vNUMA enabled and ensure the VM has enough memory to span two nodes.. Setting vNUMA controls exposes the NUMA topology to the guest OS, allowing it to optimize memory locality. By default, vNUMA is enabled for VMs with more than 8 vCPUs. Placing the VM on a single NUMA node would limit resources. Disabling hyperthreading is unnecessary. Setting CPU affinity reduces flexibility.

Answer

Disable hyperthreading on the host to reduce contention.

Answer

Assign all vCPUs to a single NUMA node using CPU affinity.

Answer

Set the VM memory reservation to zero to allow transparent page sharing.

Question 13

A vSphere administrator observes that a VM's memory usage is high, and the host memory is overcommitted. The VM has a memory balloon driver installed and running. Which metric in esxtop would the administrator check to confirm that ballooning is reclaiming memory?

Accepted Answer

MCTLSZ. The MCTLSZ field in esxtop's memory section shows the current amount of memory reclaimed by the balloon driver. ACTV shows active memory, SWCUR shows swapped memory, and VMMEMCTL shows memory control overhead. MCTLSZ directly indicates balloon activity.

Answer

SWCUR

Answer

ACTV

Answer

VMMEMCTL

Question 14

A vSphere cluster has DRS enabled and hosts with unbalanced resource usage. Which DRS feature automatically migrates VMs to balance CPU and memory loads across hosts?

Accepted Answer

Distributed Resource Scheduler (DRS). DRS (Distributed Resource Scheduler) uses vMotion to migrate VMs based on resource utilization thresholds, balancing workloads across hosts. HA provides failover, EVC ensures compatibility, and SIOC manages storage I/O.

Answer

High Availability (HA)

Answer

Enhanced vMotion Compatibility (EVC)

Answer

Storage I/O Control (SIOC)

Question 15

An administrator monitors network performance using esxtop. Which field in the network section indicates the total number of packets dropped per second due to the virtual switch being overrun?

Accepted Answer

%DRPTX. The %DRPTX field shows the percentage of transmit packets dropped because the vSwitch or physical NIC was overrun. Rx dropped is shown by %DRPRX. PKTTX is transmit packets, MPS is million packets per second.

Answer

MPS

Answer

%DRPRX

Answer

PKTTX/s