VCP-DCV vSphere Performance and Scaling Practice Test 2 — 15 Questions

Question 1

A virtualized SQL server is experiencing high latency on its virtual disks. The datastore is an NFS mount on a shared NAS. Which action would most likely reduce disk latency without reducing capacity?

Accepted Answer

Enable Storage I/O Control (SIOC) on the datastore and set the latency threshold to a lower value.. D is correct because enabling Storage I/O Control (SIOC) on the NFS datastore and lowering the latency threshold allows the hypervisor to proactively throttle I/O-intensive VMs before the storage array becomes congested, reducing overall disk latency. SIOC uses a latency-based algorithm to enforce fairness and prevent a single VM from monopolizing I/O resources, which directly addresses the high-latency issue without altering the datastore capacity.

Answer

Increase the number of outstanding I/O requests per virtual disk in the VM settings.

Answer

Disable SIOC on the datastore to avoid overhead.

Answer

Enable SIOC on the datastore and set the latency threshold to a higher value.

Question 2

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.. Option B is correct because 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 3

A vSphere administrator needs to monitor the performance of a cluster of 10 ESXi hosts. The cluster is running 200 VMs. Which tool provides real-time performance metrics and historical data with the least overhead?

Accepted Answer

vCenter Performance Charts. vCenter Performance Charts provide real-time and historical performance metrics for clusters, hosts, and VMs with minimal overhead because they query the vCenter Server database, which aggregates data from ESXi hosts at configurable intervals (default 20 seconds for real-time, 5 minutes for historical). This avoids the need for direct host connections or additional logging, making it the most efficient choice for monitoring a cluster of 10 hosts and 200 VMs.

Answer

resxtop

Answer

esxtop with output logged to a file

Answer

vRealize Operations Manager

Question 4

A company has a cluster with DRS set to Fully Automated. A VM named VM1 has a reservation of 4 GHz and a limit of 8 GHz on a host with 10 GHz available. The VM is running a batch job that requires as much CPU as possible. The administrator notices that the VM's CPU usage never exceeds 4 GHz. What is the most likely reason?

Accepted Answer

The VM has a CPU limit set to 4 GHz via a resource pool or VM override.. Option C is correct because a CPU limit explicitly caps the maximum CPU usage a VM can consume, regardless of available resources. In this scenario, the VM has a reservation of 4 GHz and a limit of 8 GHz on the host, but the administrator observes usage never exceeding 4 GHz, indicating a more restrictive limit is applied via a resource pool or VM override. This overrides the host-level limit, effectively capping the VM at 4 GHz, which matches the observed behavior.

Answer

The CPU reservation is preventing the VM from using more than the reserved amount.

Answer

The CPU shares are too low, causing the VM to be starved.

Answer

DRS is not migrating the VM to a host with more resources.

Question 5

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.

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 6

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.. NetQueue improves network performance by distributing packet processing across multiple CPUs, reducing the overhead on a single core and lowering latency for latency-sensitive VMs. This is achieved by using multiple receive queues on the physical NIC, which allows parallel packet handling and minimizes interrupt coalescing delays.

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 7

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.. Storage IOPS capacity for boot storms is critical because when 1000 desktops boot simultaneously (e.g., at start of shift), they generate a massive burst of read I/O. If the storage array cannot handle the peak IOPS, desktops will experience slow boot times or timeouts. Proper sizing must account for both steady-state IOPS and the boot storm peak, often using flash storage or caching to absorb the load.

Answer

vMotion compatibility between hosts.

Answer

NUMA alignment of virtual desktops.

Question 8

A company runs a 3-node vSAN cluster with all-flash configuration. Each host has 2 CPUs (8 cores each) and 256 GB RAM. The cluster hosts 30 VMs, including a critical database VM with 8 vCPUs and 64 GB RAM. Recently, users report that the database VM is slow during peak hours. The administrator checks vCenter performance charts and sees that the VM's CPU ready time averages 10%, and the vSAN latency spikes to 15 ms during peak hours. The storage policy for the database VM is set to RAID-1 mirroring with 2 failures to tolerate (FTT=2). The cluster is configured with 3 disk groups per host, each with one 400 GB NVMe cache SSD and two 2 TB SAS SSD capacity drives. Which action would most improve the performance of the database VM?

Accepted Answer

Change the storage policy for the database VM to RAID-1 mirroring with FTT=1 (primary level of failures to tolerate).. The database VM is experiencing high CPU ready time (10%) and vSAN latency spikes (15 ms). With FTT=2 and RAID-1 mirroring, each write must be replicated to three hosts (the primary and two mirrors), consuming significant storage and network resources. Reducing FTT to 1 lowers the write amplification from 3x to 2x, decreasing I/O latency and freeing up CPU cycles for the VM, directly addressing both symptoms.

Answer

Add one additional disk group to each host to increase storage performance.

Answer

Remove one host from the cluster to reduce network traffic.

Answer

Add a fourth host to the vSAN cluster to distribute the load.

Question 9

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

Answer

Memory Swap In Rate

Answer

Network Packet Drop Rate

Question 10

Refer to the exhibit. An administrator runs the command on an ESXi host to check HTTPS connections. The host is running vCenter Server and several VMs. What is the most likely cause of the TIME_WAIT connection?

Accepted Answer

A client closed the HTTPS connection and the host is in TIME_WAIT state.. Option D is correct because the TIME_WAIT state is a normal part of TCP connection termination. When a client closes an HTTPS connection, the ESXi host (as the server) enters TIME_WAIT to ensure any delayed segments are not misinterpreted by a new connection. This state is expected and not indicative of a problem.

Answer

A firewall is blocking return traffic from that client.

Answer

The host's TCP stack is misconfigured for high traffic.

Answer

The host is under memory pressure and dropping connections.

Question 11

A company runs a four-node vSphere 7 cluster with all-flash storage and 25GbE networking. The cluster hosts 50 VMs, including a critical database VM with 16 vCPUs and 64 GB memory. The database VM's performance has degraded over the past week. vCenter reports high CPU ready time (average 15%) for the database VM, while other VMs show less than 2%. CPU utilization on the host is 70%. The database VM is configured with CPU affinity pinned to cores 0-15 on a dual-socket host with 16 cores per socket (32 total). The administrator also notices that the database VM's CPU co-stop counter is high. What should the administrator do to improve performance?

Accepted Answer

Remove the CPU affinity setting for the database VM.. The high CPU ready time (15%) and elevated co-stop counter indicate that the database VM is suffering from contention due to CPU affinity pinning to cores 0-15. On a dual-socket host with 16 cores per socket, pinning to cores 0-15 restricts the VM to a single NUMA node, preventing the scheduler from load-balancing across both sockets. Removing the affinity allows the ESXi scheduler to distribute vCPUs across all 32 cores, reducing co-scheduling overhead and ready time.

Answer

Migrate the database VM to a host with fewer VMs.

Answer

Enable CPU hot-add for the database VM.

Answer

Increase the number of vCPUs for the database VM to 32.

Question 12

Arrange the steps to add an existing virtual machine to a vCenter Server inventory.

Question 13

Match each vSphere command-line tool to its purpose.

Question 14

A company has a cluster of 4 ESXi hosts. They want to ensure that virtual machines are automatically distributed evenly across hosts based on CPU and memory load. Which feature should be enabled on the cluster?

Accepted Answer

vSphere DRS. DRS (Distributed Resource Scheduler) automatically balances VM loads based on resource usage. HA provides high availability, FT provides fault tolerance, and DPM manages host power.

Answer

vSphere HA

Answer

Fault Tolerance

Answer

Distributed Power Management

Question 15

A vSphere administrator notices that a VM running a critical database is experiencing high latency on its virtual disk. The VM uses a VMDK on a datastore shared by several other VMs. The datastore is backed by an all-flash array. Which action would best reduce latency without increasing storage capacity?

Accepted Answer

Enable Storage I/O Control (SIOC) on the datastore. Storage I/O Control (SIOC) can enforce I/O shares and limits to prioritize latency-sensitive VMs. Increasing shares or limits may not reduce latency if the array is saturated. Moving to another datastore may not be feasible.

Answer

Increase the virtual disk shares for the VM

Answer

Move the VM to another datastore

Answer

Set a higher I/O limit on the VM