VMware VCP6-DCV 2V0-621 Questions & Answers

• Question 201:

  An administrator notices that 8 out of 10 virtual machines have memory ballooning and swapping. However, virtual machine 9 is not ballooning or swapping and virtual machine 10 is not ballooning but is swapping.

  Which two statements explain the behavior of virtual machine 9 and virtual machine 10? (Choose two.)

  A. Virtual machine 9 has a 100% memory reservation.

  B. Virtual machine 10 has a memory limit configured.

  C. Virtual machine 9 has memory shares set to HIGH.

  D. Virtual machine 10 does not have VMware Tools enabled or installed.

  Correct Answer: AD

  If the memory usage value is high, and the host has high ballooning or swapping, check the amount of free physical memory on the host. A free memory value of 6% or less indicates that the host cannot handle the demand for memory. This leads to memory reclamation, which might degrade performance. If the host has enough free memory, check the resource shares, reservation, and limit settings of the virtual machines and resource pools on the host. Verify that the host settings are adequate and not lower than those set for the virtual machines. D-) Verify that VMware Tools is installed on each virtual machine. The balloon driver is installed with VMware Tools and is critical to performance. If Vmware tools are not installed/outdated showing on summary tab Ballooning will not work hence swapping will work because it has nothing to do with ballooning. Fact: If memory is not available the memory can med mapped to the .vswp file on a vmfs or nfs datastore. The virtual machine has no knowledge if the memory is mapped to physical memory or to a disk. This is called hypervisor swapping, and this is the last resort for the vmkernel to use this mechanism.(Internal vmware KB article but for external you may check VMBlog or external links: https://kb.vmware.com/ selfservice/microsites/search.do? language=en_USandcmd=displayKCandexternalId=1003470)

• Question 202:

  An administrator is troubleshooting a CPU issue for a virtual machine. The following is seen in esxtop:

  1.

  CPU0 is at 100% usage

  2.

  The remaining logical CPUs are close to 0%

  3.

  %RDY value is consistently above 10%

  What is likely the cause of the CPU issue?

  A. The virtual machine has a CPU limit configured.

  B. The virtual machine's guest operating system is configured for SMP.

  C. The virtual machine has CPU affinity configured.

  D. The virtual machine is configured with a CPU reservation.

  Correct Answer: C

  Using CPU Affinity

  By specifying a CPU affinity setting for each virtual machine, you can restrict the assignment of virtual

  machines to a subset of the available processors in multiprocessor systems. By using this feature, you can

  assign each virtual machine to processors in the specified affinity set.

  CPU affinity specifies virtual machine-to-processor placement constraints and is different from the

  relationship created by a VM-VM or VM-Host affinity rule, which specifies virtual machine-to-virtual

  machine host placement constraints.

  Reference:

  https://pubs.vmware.com/vsphere-4-esx-vcenter/index.jsp?topic=/

  com.vmware.vsphere.resourcemanagement.doc_41/managing_cpu_resources/c_using_cpu_affinity.html

• Question 203:

  An administrator observes the following symptoms for a virtual machine:

  1.

  CPU usage is consistently above 90%

  2.

  CPU ready value is consistently above 20%.

  3.

  Application performance is impacted.

  Which two actions should the administrator take to improve the performance of this virtual machine? (Choose two.)

  A. Increase the number of vCPUs assigned to this virtual machine.

  B. Decrease the number of vCPUs assigned to this virtual machine.

  C. Verify that VMware Tools is installed on every virtual machine on the host.

  D. Increase the CPU shares assigned to the virtual machine.

  Correct Answer: CD

  Solutions for Consistently High CPU Usage Temporary spikes in CPU usage indicate that you are making the best use of CPU resources. Consistently high CPU usage might indicate a problem. You can use the vSphere Client CPU performance charts to monitor CPU usage for hosts, clusters, resource pools, virtual machines, and vApps. Problem

  Host CPU usage constantly is high. A high CPU usage value can lead to increased ready time and processor queuing of the virtual machines on the host. Virtual machine CPU usage is above 90% and the CPU ready value is above 20%. Application performance is impacted. Cause The host probably is lacking the CPU resources required to meet the demand. Solution Verify that VMware Tools is installed on every virtual machine on the host. Compare the CPU usage value of a virtual machine with the CPU usage of other virtual machines on the host or in the resource pool. The stacked bar chart on the host's Virtual Machine view shows the CPU usage for all virtual machines on the host. Determine whether the high ready time for the virtual machine resulted from its CPU usage time reaching the CPU limit setting. If so, increase the CPU limit on the virtual machine. Increase the CPU shares to give the virtual machine more opportunities to run. The total ready time on the host might remain at the same level if the host system is constrained by CPU. If the host ready time doesn't decrease, set the CPU reservations for high-priority virtual machines to guarantee that they receive the required CPU cycles. Increase the amount of memory allocated to the virtual machine. This action decreases disk and or network activity for applications that cache. This might lower disk I/O and reduce the need for the host to virtualize the hardware. Virtual machines with smaller resource allocations generally accumulate more CPU ready time. Reduce the number of virtual CPUs on a virtual machine to only the number required to execute the workload. For example, a single-threaded application on a four-way virtual machine only benefits from a single vCPU. But the hypervisor's maintenance of the three idle vCPUs takes CPU cycles that could be used for other work. If the host is not already in a DRS cluster, add it to one. If the host is in a DRS cluster, increase the number of hosts and migrate one or more virtual machines onto the new host. Upgrade the physical CPUs or cores on the host if necessary. Use the newest version of hypervisor software, and enable CPU-saving features such as TCP Segmentation Offload, large memory pages, and jumbo frames.

  Reference: https://pubs.vmware.com/vsphere-51/index.jsp?topic=%2Fcom.vmware.vsphere.monitoring.doc%2FGUID5F8147A1-6416-4D29-BA3D-E4CED3966016.html

• Question 204:

  When troubleshooting a performance related issue, an administrator sees the following warning message on an ESXi Console:

  Significant imbalance between NUMA nodes detected. Performance may be impacted.

  Which action should the administrator take to correct this problem?

  A. Ensure that the RAM modules are evenly balanced between processor sockets in the physical server.

  B. Ensure that all memory banks associated with CPU Socket 0 in the physical server are completely filled.

  C. Ensure that the physical server has the maximum amount of RAM modules that it can support.

  D. Ensure that all RAM modules in the host are Error-correcting code (ECC) modules.

  Correct Answer: A

  This message displays when memory is not evenly distributed between processor sockets.

  Each CPU socket has its own RAM slots. To resolve this issue, evenly balance RAM modules between

  processor sockets. That is, ensure that each bank of RAM slots has the same amount of RAM.

  For example, if CPU socket 1 has a total of 8 GB of RAM, ensure that CPU socket 2 also has 8 GB of

  RAM.

  Ensure that memory on the nodes are balanced. For more information and assistance, contact your

  vendor.

  Note: Damaged or faulty physical RAM modules can also cause this issue.

  Reference:

  https://kb.vmware.com/selfservice/microsites/search.do?

  language=en_USandcmd=displayKCandexternalId=1018754

• Question 205:

  An administrator has a virtual machine configured with the following settings:

  1.

  ESXi version: 5.1

  2.

  CPU: vCPUs 6

  3.

  Memory: 48GB

  4.

  Hardware version: 7

  5.

  VMware Tools: Installed

  Which two actions must the administrator take in order to utilize vNUMA? (Choose two.)

  A. Upgrade the ESXi host to vSphere 5.5 or later.

  B. Upgrade to Virtual Hardware version 8.

  C. Configure numa.vcpu.min to 5

  D. Configure numa.vcpu.min to 6

  Correct Answer: BD

  Using Virtual NUMA vSphere 5.0 and later includes support for exposing virtual NUMA topology to guest operating systems, which can improve performance by facilitating guest operating system and application NUMA optimizations. Virtual NUMA topology is available to hardware version 8 virtual machines and is enabled by default when the number of virtual CPUs is greater than eight. You can also manually influence virtual NUMA topology using advanced configuration options. You can affect the virtual NUMA topology with two settings in the vSphere Client: number of virtual sockets and number of cores per socket for a virtual machine. If the number of cores per socket (cpuid.coresPerSocket) is greater than one, and the number of virtual cores in the virtual machine is greater than 8, the virtual NUMA node size matches the virtual socket size. If the number of cores per socket is less than or equal to one, virtual NUMA nodes are created to match the topology of the first physical host where the virtual machine is powered on. Reference: https://pubs.vmware.com/vsphere-51/index.jsp#com.vmware.vsphere.resmgmt.doc/GUID-17B629DE75DF-4C23-B831-08107007FBB9.html

  --------------note----------------------Also, Check Page 21,22 https://www.vmware.com/pdf/Perf_Best_Practices_vSphere5.1.pdf D-) Size your virtual machines so they align with physical NUMA boundaries. For example, if you have a host system with six cores per NUMA node, size your virtual machines with a multiple of six vCPUs (i.e., 6 vCPUs, 12 vCPUs, 18 vCPUs, 24 vCPUs, and so on). Hence answer is D Also, Check Page 41,42 https://www.vmware.com/pdf/Perf_Best_Practices_vSphere5.1.pdf

• Question 206:

  An administrator is troubleshooting a performance problem with a virtual machine (VM). The VM and ESXi host configuration is as follows:

  1.

  The application which runs within the virtual machine is highly sensitive to memory latency, but has low processor utilization.

  2.

  The virtual machine has 6 vCPUs.

  3.

  The ESXi host CPU topology has 2 Physical CPU Sockets, each with 8 Logical CPUs.

  4.

  The ESXi host CPU has Hyper Threading enabled.

  The administrator would like to improve CPU performance for this VM. Other VMs on the host have no performance issues. Which action should the administrator take to resolve the issue?

  A. Set the Advanced Parameter numa.vcpu.preferHT = TRUE in the virtual machine configuration file.

  B. Set the Advanced Parameter numa.vcpu.preferHT = FALSE in the virtual machine configuration file.

  C. Set the Advanced Parameter numa.PreferHT = 1 in the ESXi host configuration file.

  D. Set the Advanced Parameter numa.PreferHT = 0 in the ESXi host configuration file.

  Correct Answer: A

  

  Reference: https://books.google.co.in/books?id=GnVvAwAAQBAJandpg=PA78andlpg=PA78anddq=Advanced+Parameter +numa.vcpu.preferHTandsource=blandots=o9dp9BqWjandsig=XT1BXwxJ6qeTg__zHfO8uLnZNToandhl=enandsa=Xandved=0ahUKEwjUyeejcrNAhWGqY8KHQCKBzwQ6AEIVjAH#v=onepageandqandf=false

• Question 207:

  Users are reporting CPU related performance problems on the virtual machine Email-Prod throughout the day.

  The resource settings for the VM and the ESXi host the VM is running on are shown below: VM:

  1.

  Email-Prod

  2.

  vCPUs: 4

  3.

  Memory: 96GB

  ESXi host:

  1.

  CPU: 2 x 8 Core Processors

  2.

  Memory: 128GB

  3.

  NUMA architecturE. 2 Nodes

  Which two options would alleviate the observed performance problem for Email-Prod? (Choose two.)

  A. Enable the advanced parameter Numa.PageMigEnable.

  B. Enable the advanced parameter Numa.AutoMemAffinity.

  C. Enable CPU affinity to separate 2 vCPUs for each NUMA node.

  D. Enable CPU affinity to bind all vCPUs to one NUMA node.

  Correct Answer: BC

  B-) Memory

  You can change the amount of RAM that a VM will use like this

  memsize = "128"

  If you don't assign a value for memory VMware will use the default-setting which is 32MB

  memsize = "32"

  Whenever you assign RAM manually make sure the value is a multiple of 4 - otherwise the VM will not

  start:

  memsize = "255"

  causes this error-message:

  Memory size 255 not a multiple of 4

  https://pubs.vmware.com/vsphere-60/index.jsp#com.vmware.vsphere.hostclient.doc/GUID-99E66B5953A8-42D0-A08F-17DBE7D4A864.html?resultof=%2522

  C-) This is expected behavior based on the current architecture of the scheduler. However, these points

  help to limit the impact of the issue :Lower the number of vCPUs. From the example above, you would

  lower the number of vCPUs from 8 to 6 or less. If the virtual machines are sized such that they are a whole

  multiple or divisor of the NUMA node size, this helps with the number of virtual machines that you can

  power on. If 6 vCPU virtual machines are used, you can run up to at least 8 of those virtual machines (with

  100% CPU utilization) without incurring substantial ready times.

  https://www.vmware.com/files/pdf/.../VMware-PerfBest-Practices-vSphere6-0.pdf

• Question 208:

  An administrator is troubleshooting a CPU performance issue for a virtual machine.

  Which three esxtop counters may demonstrate CPU contention? (Choose three.)

  A. %RDY

  B. %RUN

  C. %MLMTD

  D. %WAIT

  E. %CSTP

  Correct Answer: ACE

  "%RDY"

  The percentage of time the world was ready to run.

  A world in a run queue is waiting for CPU scheduler to let it run on a PCPU. %RDY accounts the

  percentage of this time. So, it is always smaller than 100%.

  +Q: How do I know CPU resource is under contention?+

  +A: %RDY is a main indicator. But, it is not sufficient by itself.+

  +If a "CPU Limit" is set to a VM's resource settings, the VM will be deliberately held from scheduled to a

  PCPU when it uses up its allocated CPU resource. This may happen even when there is plenty of free

  CPU cycles. This time deliberately held by scheduler is shown by "%MLMTD", which will be describe next.

  Note that %RDY includes %MLMTD. For, for CPU contention, we will use "%RDY - %MLMTD". So, if "%

  RDY - %MLMTD" is high, e.g., larger than 20%, you may experience CPU contention.+

  +What is the recommended threshold? Well, it depends. As a try, we could start with 20%. If your

  application speed in the VM is OK, you may tolerate higher threshold. Otherwise, lower.+

  +Q: How do we break down 100% for the world state times?+

  +A: A world can be in different states, either scheduled to run, ready to run but not scheduled, or not ready

  to run (waiting for some events).+ 100% = %RUN + %READY + %CSTP + %WAIT.

  +Check the description of %CSTP and %WAIT below.+

  +Q: What does it mean if %RDY of a VM is high?+

  +A: It means the VM is possibly under resource contention. Check "%MLMTD" as well. If "%MLMTD" is

  high, you may raise the "CPU limit" setting for the VM. If "%RDY - %MLMTD" is high, the VM is under CPU

  contention.+

  "%MLMTD"

  The percentage of time the world was ready to run but deliberately wasn't scheduled because that would

  violate the "CPU limit" settings.

  Note that %MLMTD is included in %RDY.

  +Q: What does it mean if %MLMTD of a VM is high?+

  +A: The VM cannot run because of the "CPU limit" setting. If you want to improve the performance of this

  VM, you may increase its limit. However, keep in mind that it may reduce the performance of others.+

  "%CSTP"

  The percentage of time the world spent in ready, co-deschedule state. This co-deschedule state is only

  meaningful for SMP VMs. Roughly speaking, ESX CPU scheduler deliberately puts a VCPU in this state, if

  this VCPU advances much farther than other VCPUs.

  +Q: What does it mean if %CSTP is high?+

  +A: It usually means the VM workload does not use VCPUs in a balanced fashion. The VCPU with high %

  CSTP is used much more often than the others. Do you really need all those VCPUs? Do you pin the guest

  application to the VCPUs?+ Reference:

  https://communities.vmware.com/docs/DOC-9279

• Question 209:

  A failed upgrade from vCenter Server version 5.x to version 6.0 produces the following error:

  [00800 error 'Default'] Database version id '600' is incompatible with this release of VirtualCenter.

  What is the cause of the upgrade failure?

  A. There was a database schema upgrade failure during the installation.

  B. The VMWAREVCMSDS service was upgraded before the vCenter Server service.

  C. The VMware Directory Service database failed during the installation.

  D. There was an incompatible ODBC driver version for the database.

  Correct Answer: A

  Explanation: Attempts to upgrade the VMware vCenter Server from 5.x to 6.0 might fail when validating the database Upgrading VMware vCenter Server with an Oracle Database from 5.x to 6.0 might fail. This error occurs when you install a vCenter Server against an external Microsoft SQL database. You need to create the database schema manually by referencing to the information in DB_and_schema_creation_scripts_mssql.txt in the DB scripts folder. An error message similar to the following is displayed: The user associated with the DSN has insufficient privileges. This issue is resolved in this release.VMware vCenter Server 6.0 Update 1 check release notes whitepaper on vmware.com Upgrading from vSphere 5.x to vSphere 6.0 Best Practices (2130664) https://kb.vmware.com/selfservice/search.do? cmd=displayKCanddocType=kcanddocTypeID=DT_KB_1_1andexternalId=2130664

• Question 210:

  Attempting to update an ESXi 6.x host using the following command:

  esxcli software vib update -d update.zip

  Generates the following error:

  Could not download from depot at /tmp/index.xml, skipping (('/tmp/index.xml', '', "[Errno 4] IOError: ")) url = /tmp/index.xml

  What action should be taken to correct the problem?

  A. Add the full file path to the command.

  B. Use the update option instead of install.

  C. Use the switch -d instead of -v.

  D. Replace esxcli with esxupdate.

  Correct Answer: A

  Put the full path to the .zip even if you're in the same directory ex: esxcli software vib install -d /tmp/ESXi600-201504001.zip Also make sure you're in maintenance mode How to perform next/related steps: Check:----https://pubs.vmware.com/vsphere-60/ index.jsp#com.vmware.vsphere.upgrade.doc/GUID-22A4B153-CB21-47B4-974E-2E5BB8AC6874.html? resultof=%2522