Section 8 – Perform Basic Troubleshooting and Alarm Management
- Objective 8.5 – Perform Basic Troubleshooting for HA/DRS and VMotion
A VM using VMDirectPath I/O cannot be VMotioned?
VMDirectPath I/O for virtual machines. Enhance CPU efficiency for applications that require frequent access to I/O devices by allowing select virtual machines to directly access underlying hardware devices. Other virtualization features, such as VMware available to the virtual machines using this feature
What is the meaning of a red, or critical, indicator on a DRS cluster?
A.At least one host in the cluster is attempting to go into Maintenance Mode
B.Yellow clusters will become red after 15 minutes if DRS is unable to dynamically balance the load
C.Red clusters indicate virtual machines are using more resources than the fixed reservation allows
D.Red clusters are the highest priority and will receive resource allocations first
Red DRS Cluster
A cluster enabled for DRS becomes red when the tree is no longer internally consistent and does not have enough resources available. For example, a DRS cluster turns red if the virtual machines in a fixed resource pool use more resources than the Reservation of that resource pool allows.
Raw Device Mapping using Physical Compatibility Mode is supported with which of the following vSphere features (Choose Two)?
A.Virtual Machine Snapshots
B.High Availability (HA)
Mastering VMware vSphere 4, page 270-1.
Physical compatibility mode (pRDM)
The inability to take a native Vmware snapshot of a pRDM also means that features that depend on Vmware snapshots (the vStorage API’s for Data Protection, Vmware Data Recovery, and Storage vMotion) don’t work with pRDMs.
VMware – Raw Device Mapping (RDM)
With Physical compatibility mode you VM can access LUN directly. This is generally used from the application inside VM wants to directly access LUN. However using physical compatibility mode you lose the option to clone a VM, make it a template and migration when it involves moving disks.
Which of the following conditions could prevent HA from powering on a virtual machine (Choose Two)?
A.The VM has a low priority setting
B.Strict admission control is configured
C.The target host is not compatible with the virtual machine
D.The VM is connected to the ESX Host CD-ROM drive
vSphere Availability Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0, page 13.
Admission control imposes constraints on resource usage and any action that would violate these constraints is not permitted. Examples of actions that could be disallowed include:
Powering on a virtual machine.
Migrating a virtual machine onto a host or into a cluster or resource pool.
Increasing the CPU or memory reservation of a virtual machine.
vSphere Availability Guide ESX 4.0 ESXi 4.0 vCenter Server 4.0, page 22.
VM restart priority determines the relative order in which virtual machines are restarted after a host failure. Such virtual machines are restarted sequentially on new hosts, with the highest priority virtual machines first and continuing to those with lower priority until all virtual machines are restarted or no more cluster resources are available.
It appears that a virtual machine (VM) in a DRS Cluster is having performance problems because it does not have enough CPU resources available.
Which of the following methods could be used to improve performance and reduce CPU contention of this VM while maintaining compatibility with DRS (Choose Two)?
A.increase CPU shares for this VM to High
B.set the CPU reservation for this VM to the Average CPU Utilization and the CPU limit for this VM to Peak CPU Utilization
C.set CPU affinity on the VM
D.set the CPU reservation for this VM to 100%
Assume the VMs CPU usage on the host looks like this currently
Assume the cluster has 4000 GHz total CPU available, and that currently the VM has 1000 MHz reserved to it, and peaks at 2000 MHz.
vSphere Basic System Administration vCenter Server 4.0 ESX 4.0 ESXi 4.0, page 155.
The values Low, Normal, High, and Custom are compared to the sum of all shares of all virtual machines on the server. Therefore if you increase CPU shares for this VM to High, it will gain proportionally more resources, improve performance and reduce CPU contention. Therefore A is correct.
If you set the CPU reservation for this VM to the Average CPU Utilization, (which will be a value between 1000 MHz and 2000 MHz) and the CPU limit for this VM to Peak CPU Utilization 2000 MHz. This will cause the VM to gain additional resources, and should improve performance. Therefore B is correct.
In general, don’t specify affinity rules unless you have specific reasons to do so. This will give DRS the maximum flexibility to consider all options for resource management and hence enable the most efficient resource placement. Setting CPU affinity will not increase available resources. Therefore C is incorrect.
Resource Management and DRS Best Practices
The following guidelines can help you achieve optimal performance for your virtual machines:
When specifying the reservations for virtual machines, always leave some headroom; do not commit all resources. As you move closer to fully reserving all capacity in the system, it becomes increasingly difficult to make changes to reservations and to the resource pool hierarchy without violating admission control. In a DRS-enabled cluster, reservations that fully commit the capacity of the cluster or of individual hosts in the
cluster can prevent DRS from migrating virtual machines between hosts. Therefore D is incorrect.
A virtual machine has been created with a guest OS virtual disk in one datastore and a data virtual disk in another datastore. Snapshots are being used on the virtual machine. Under which of the following conditions can the virtual machine be successfully migrated (Choose Two)?
A.When using Cold Migration to move between AMD and Intel CPUs
B.When using Cold Migration to move the Virtual Machine to a different datastore(s)
C.When using Storage VMotion
D.When using VMotion migration
When using Cold Migration, migration between AMD and Intel CPUs is allowed – so A is correct
When using Cold Migration, migration between change of datastore is allowed – so B is correct
When using VMotion migration VMs with snapshots cannot be migrated – so D is incorrect
vSphere Basic System Administration vCenter Server 4.0 ESX 4.0 ESXi 4.0, page 196
Storage VMotion Requirements and Limitations
A virtual machine and its host must meet resource and configuration requirements for the virtual machine disks to be migrated with Storage VMotion.
Storage VMotion is subject to the following requirements and limitations:
Virtual machines with snapshots cannot be migrated using Storage VMotion. – so C is incorrect
During an attempt to create a new ABC resource pool in a cluster, the New Resource Pool selection appears to be unavailable. What could be the cause?
A.DRS has not been enabled on the cluster
B.The cluster has too few resources to create a new resource pool
C.There are no servers in the cluster
D.VMware HA has not been enabled on the cluster
When attempting to VMotion migrate a newly built running virtual machine, the migration fails. Which of the following conditions would cause a failed migration under these conditions?
A.The number of processor cores differs between the source and target hosts
B.The source host supports hyperthreading, but the target host does not
C.NPIV has been enabled on the virtual machine, and VMotion is not supported with NPIV
D.VMI Paravirtualization Support has been enabled for the virtual machine, but is not supported on the target host
Migrating VMI-enabled virtual machines to platforms that do not support VMI
If you have suspended a virtual machine that uses VMI on an earlier release of a VMware product, you cannot resume the virtual machine on a VMware product which does not support VMI.
You cannot vMotion VMI-enabled virtual machines from earlier releases to future products that do not support VMI.
Instead, use cold migration to transition the VMI-enabled virtual machine to a future VMware product. Power the virtual machine off and then power it back on in the future VMware product.
Which of the following steps are required to successfully install VMware Data Recovery (Choose Two)?
A.A shared backup disk or tape device must be designated
B.The VMware Data Recovery Backup Appliance must be installed to a managed ESX Host
C.The Client Plug-in must be installed in the vSphere Client
D.The VMware Data Recovery server component must be installed on the vCenter Server
VMware® Data Recovery 1.0 Evaluator’s Guide, page 9.
You have to ensure the VMware Data Recovery Plug-In has been properly installed, and the backup appliance has been properly imported and configured before proceeding.
An administrator has a 6 node DRS cluster. Using vCenter Update Manager, what is the maximum number of host upgrade operations that can be performed at any given time in this cluster?
Mastering VMware vSphere 4, page 126.
Table 4.1: Limits for vCenter Update Manager