VCP-DCV vSphere Performance and Scaling Practice Test 4 — 15 Questions

Question 1

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?

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

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 2

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. %DRPTX shows the percentage of transmit packets dropped due to vSwitch or physical NIC overrun. Although the stem asks for 'total number per second,' %DRPTX is the only field among the options that measures dropped packets caused by overrun. It updates per sampling interval, effectively indicating the drop rate. The other options are either for receive drops (%DRPRX) or unrelated counts (MPS, PKTTX/s).

Answer

MPS

Answer

%DRPRX

Answer

PKTTX/s

Question 3

A vSphere administrator notices that a VM is performing poorly on a host with multiple NUMA nodes. The VM has 16 vCPUs and 64 GB of memory, but the host has only 32 GB of memory per NUMA node. Which action would MOST LIKELY improve performance?

Accepted Answer

Enable vNUMA in the VM settings.. When a VM's memory footprint (64 GB) exceeds the memory available per NUMA node (32 GB), the VM spans multiple NUMA nodes, causing remote memory access latency. Enabling vNUMA exposes the host's NUMA topology to the guest OS, allowing it to optimize vCPU and memory placement and schedule threads locally, which reduces cross-node traffic and improves performance.

Answer

Increase the memory reservation to 64 GB.

Answer

Reduce the number of vCPUs to 8.

Answer

Migrate the VM to a host with more memory per NUMA node.

Question 4

A database VM with 32 vCPUs and 256 GB memory is deployed on a host with two NUMA nodes, each with 8 cores (16 threads with HT). The application performs badly. Analysis shows high remote memory access. What is the MOST LIKELY reason?

Accepted Answer

The vNUMA nodes are not aligned with the physical NUMA nodes.. The VM has 32 vCPUs, but each physical NUMA node only has 8 cores (16 threads). Since a vNUMA node cannot span physical NUMA nodes without incurring remote access, the VM's vNUMA topology likely does not match the underlying hardware. When vNUMA is not aligned, vCPUs and memory are placed across both physical nodes, causing frequent remote memory accesses and poor performance. Proper alignment would require the VM's vNUMA nodes to correspond exactly to the physical NUMA nodes (e.g., two vNUMA nodes of 16 vCPUs each), ensuring local memory access.

Answer

Hyperthreading is enabled causing CPU contention.

Answer

The host's NUMA nodes are not balanced in memory capacity.

Answer

The VM has too much memory allocated.

Question 5

Which THREE memory-related metrics in esxtop indicate that a virtual machine is experiencing memory pressure? (Choose three.)

Accepted Answer

SWCUR. SWCUR (current swapped memory) indicates that the VM has swapped memory to disk, a clear sign of memory pressure. MCTLSZ (memory balloon driver size) shows the amount of memory reclaimed by the balloon driver due to contention, also indicating pressure. ACTV (active memory) when high relative to the VM's configured memory can indicate that the VM is actively using memory and may be under pressure, especially when combined with other metrics. %SYS and %RDY are CPU-related metrics and not relevant to memory pressure.

Answer

%SYS

Answer

%RDY

Question 6

Based on the exhibit, which statement about the virtual machine's memory state is TRUE?

Accepted Answer

The VM is actively swapping memory because of memory pressure.. The exhibit (not shown, but typical of a VM memory performance chart) indicates active swapping, which occurs when the VM's memory demand exceeds its configured memory and the hypervisor must swap VM pages to disk. This is a sign of memory pressure and degraded performance. The correct answer is that the VM is actively swapping due to memory pressure.

Answer

The VM is using the memory balloon driver to reclaim memory.

Answer

The VM is using transparent page sharing to reduce memory usage.

Answer

The VM has no memory pressure and is performing optimally.

Question 7

Based on the exhibit, which statement about vNUMA exposure to virtual machines is correct?

Accepted Answer

VMs with 6 vCPUs will have vNUMA exposed.. The settings define that vNUMA is exposed to VMs with vCPUs between minPerMachine (4) and maxPerMachine (8) inclusive. Therefore, a VM with 6 vCPUs will have vNUMA topology exposed. VMs with fewer than 4 vCPUs will not have vNUMA, and VMs with more than 8 vCPUs will also not have vNUMA exposed because maxPerMachine is 8.

Answer

The settings are invalid because minPerMachine must be greater than maxPerMachine.

Answer

VMs with 6 vCPUs will not have vNUMA exposed.

Answer

Only VMs with exactly 4 or 8 vCPUs will have vNUMA exposed.

Question 8

A company's vSphere environment experiences intermittent performance degradation on a critical virtual machine. The VM has 8 vCPUs allocated, and the host has 16 physical cores (2 sockets, 8 cores each). The VM is configured with Hyper-Threading enabled. Which action is most likely to improve performance without increasing resource allocation?

Accepted Answer

Change the VM's CPU affinity to pin it to one socket. Pinning the VM to one socket reduces NUMA cross-socket latency, improving performance for the 8-vCPU VM. Option B is wrong because CPU hot-add does not improve performance; it allows adding CPUs later. Option C is wrong as memory reservation does not directly affect CPU performance. Option D is wrong because disabling Hyper-Threading generally reduces throughput.

Answer

Enable CPU hot-add for the VM

Answer

Increase the VM's memory reservation

Answer

Disable Hyper-Threading on the host

Question 9

A vSphere administrator notices high memory ballooning on a host running multiple VMs with large memory allocations. The host has sufficient physical memory, but ballooning occurs sporadically. What is the most likely cause?

Accepted Answer

The VM's memory limit is set too low. Memory ballooning occurs when the VM's configured memory limit is lower than its assigned memory. The balloon driver reclaims memory from the guest to enforce the limit, even if the host has plenty of free physical memory. This sporadic ballooning is a direct result of the limit being set too low relative to the VM's active memory usage.

Answer

The host is overcommitted on CPU

Answer

The VM's memory is set to a reservation higher than the physical memory

Answer

The host has insufficient swap space

Question 10

An administrator wants to maximize performance for a latency-sensitive application running on a VM. The host has two NUMA nodes. Which vSphere feature should be configured to ensure the VM's memory is allocated from the same NUMA node as its vCPUs?

Accepted Answer

NUMA affinity. NUMA affinity ensures that a VM's memory is allocated from the same NUMA node as its vCPUs, minimizing remote memory access latency. This is critical for latency-sensitive applications because cross-NUMA memory access incurs higher latency and lower bandwidth.

Answer

Memory reservation

Answer

CPU affinity

Answer

Memory latency sensitivity

Question 11

An administrator observes that a VM with 16 vCPUs on a 2-socket host (8 cores per socket, HT disabled) is experiencing poor performance. The VM's NUMA topology shows 2 vNUMA nodes, but performance is worse than expected. What is the most likely reason?

Accepted Answer

The VM is configured with a single virtual socket with 16 cores, causing the vNUMA nodes to span both physical NUMA nodes and lead to remote memory accesses.. When a VM is configured with a single virtual socket containing 16 cores, vSphere presents two vNUMA nodes to the guest, but these nodes span both physical NUMA nodes. This causes the guest OS to schedule memory accesses across NUMA boundaries, leading to remote memory latency and poor performance. The correct configuration is to match the virtual socket count to the physical NUMA topology, e.g., two virtual sockets with 8 cores each.

Answer

The VM's memory is reserved but not backed by physical pages

Answer

The virtual hardware version is too old

Answer

The host has insufficient RAM

Question 12

A vSphere administrator is troubleshooting a VM that shows high 'CPU ready' time in vCenter performance charts. The host has 32 logical CPUs (16 cores with HT). Which tool should be used to identify which other VMs are contending for CPU resources?

Accepted Answer

Esxtop with CPU world view. Esxtop with the CPU world view (press 'c' for CPU, then 'e' to expand worlds, and 'u' for world view) allows the administrator to see per-world CPU scheduling statistics, including which VMs are consuming CPU and contributing to ready time. This is the native vSphere tool for diagnosing CPU contention at the world level. It provides detailed metrics such as %RDY, %CSTP, and %MLMTD for each world.

Answer

vRealize Operations Manager

Answer

Resxtop with CPU view

Answer

vCenter Resource Allocation chart

Question 13

An administrator configures a resource pool with a reservation of 10 GHz and a limit of 20 GHz. The pool contains two VMs: VM1 has a reservation of 6 GHz and no limit, VM2 has no reservation and a limit of 8 GHz. The host has only 12 GHz available. During peak usage, both VMs demand more than their shares. Which statement is true?

Accepted Answer

VM1 gets at least 6 GHz, VM2 gets at most 8 GHz, but because the pool limit is 20 GHz and host only 12, VM2's limit is effectively 6 GHz after VM1's reservation. VM1's 6 GHz reservation is guaranteed first, leaving 6 GHz of the host's 12 GHz for VM2. VM2's own limit is 8 GHz, but the pool's effective ceiling is the host's 12 GHz, so after VM1's reservation VM2 can use at most 6 GHz. The pool limit of 20 GHz is irrelevant because the physical host only has 12 GHz.

Answer

VM1 gets at least 6 GHz, VM2 gets at most 8 GHz, and the remaining 4 GHz is divided by share

Answer

VM1 gets exactly 6 GHz, VM2 gets exactly 8 GHz, and the pool's reservation is ignored

Answer

VM1 gets at least 6 GHz, VM2 gets at least 2 GHz due to pool reservation, and both use remaining as share

Question 14

A vSphere cluster uses vSAN with deduplication and compression enabled. An administrator notices that IOPS for a VM is lower than expected despite low CPU and memory utilization on hosts. Which of the following is most likely the cause?

Accepted Answer

Deduplication and compression overhead is causing increased CPU usage on storage controller. When deduplication and compression are enabled on a vSAN cluster, the storage controller must perform inline dedup and compression operations on every write, which consumes CPU cycles on the host. If the storage controller CPU becomes a bottleneck, I/O operations queue and effective IOPS for the VM drops even though general host CPU and memory utilization appear low. This is the classic symptom of dedup/compression overhead limiting storage throughput.

Answer

The VM storage policy has no read cache reservation

Answer

vSAN object repair is consuming disk bandwidth

Answer

The VM is running on a host with a vSAN disk capacity tier that is 80% full

Question 15

An administrator configures a VM with 4 vCPUs and 32 GB memory on a host with 128 GB RAM and 8 cores (HT enabled). The VM runs a database that requires high memory bandwidth. Performance monitoring shows low CPU usage but high memory latency. Which configuration change is most likely to improve memory performance?

Accepted Answer

Enable the 'Preferred NUMA Node' VM option. Preferred NUMA Node allows the VM to be pinned to a specific NUMA node, reducing cross-node memory access. Option B is wrong; increasing reservation does not improve latency. Option C is wrong; disabling HT reduces overall throughput. Option D is wrong; more vCPUs may increase contention.

Answer

Increase the memory reservation to 64 GB

Answer

Disable Hyper-Threading on the host

Answer

Increase the number of vCPUs to 8