Objective 4.3 Topics:

• Analyze and Resolve DRS/HA faults
• Troubleshoot DRS/HA Configuration Issues
• Troubleshoot Virtual SAN/HA Interoperability
• Resolve vMotion and Storage vMotion Issues
• Troubleshoot VMware Fault Tolerance

Analyze and Resolve DRS/HA Faults

DRS faults indicate the reason that prevent DRS actions.

DRS Faults

Virtual Machine is Pinned – When DRS can’t move a VM because DRS is disabled on the VM.

Virtual Machine Not Compatible with ANY Host – Fault occurs when DRS can’t find a host that can run the VM. This might mean that there are not enough physical compute resources or disk available to satisfy the VM’s requirements.

VM/VM DRS Rule Violated When Moving to Another Host – Fault occurs when more that one virtual machines running on the same host are use the same affinity rule

Host Incompatible with Virtual Machine – Fault occurs when trying to migrate a VM to which the destination host might not have access to network or storage needed to maintain connectivity on the VM. A second reason this might occur is that the CPU’s are vastly different between the hosts that vMotion is not supported. And thirdly, is that there is a required VM/Host DRS rule in place that tells DRS to never move this particular VM.

Host has Virtual Machine That Violates VM/VM DRS Rules – Occurs when moving or powering on a VM that has a VM/VM DRS rule. Machine can still be moved if done so manually. vCenter just will not do it automatically.

Host has Insufficient Capacity for Virtual Machine – Occurs when the host does not have enough compute or memory to satisfy the VM’s requirements.

Host in Incorrect State – Occurs when a host is entering maintenance or standby state when it’s needed for DRS.

Host has Insufficient Number of Physical CPU’s for a Virtual Machine – When the VM has more physical CPU’s than the host has available.

Host has Insufficient Capacity for Each Virtual Machine CPU – Occurs when the VM has more virtual CPU’s than the host has available.

No Active Host in Cluster – Occurs when moving a virtual machine to a cluster that doesn’t have any available hosts that are connected and available.

Insufficient Resources – Occurs when a operation conflicts with a resource configuration policy. Example: If you try to power on a 4GB VM in a 2GB resource pool with a limit/not expandable.

Insufficient Resources to Satisfy Configured Fail-over Level for HA – Occurs when the HA configuration of CPU or memory resources are reserved for failover (Admission Control) is violated or can’t be met by the DRS operation. This can occur when a host is trying to enter maintenance mode or standby mode or when a VM violates fail-over when it attempts to power on.

No Compatible Hard Affinity Host – No host available to satisfy a mandatory VM/Host DRS affinity/anti-affinity rule.

No Compatible Soft Affinity Host – No host available to satisfy a preferred VM/Host DRS affinity/anti-affinity rule.

Soft Rule Violation Correction Disallowed – DRS migration threshold is set to mandatory only. This does not allow the generation of DRS actions to correct a non-mandatory VM/Host DRS affinity rule.

Soft Rules Violation Correction Impact – Correcting the non-mandatory VM/Host DRS affinity rules does not occur because it impacts performance.

 

Troubleshoot DRS/HA Configuration Issues

Troubleshooting Steps:

1. Check for known issues. vSphere isn’t perfect but it’s close. 😉
2. Ensure that HA is properly configured.
3. Verify that network connectivity is working between the hosts and vCenter.
4. Verify that the hosts are properly connected to vCenter.
5. Verify the datastore used for heart-beating is accessible by all the hosts in the cluster.
6. Verify that all the configuration files of the FDM agent were pushed successfully to the hosts.
   1. Log location of hosts: /etc/opt/vmware/fdm
7. Increase the FDM log output to verbose.

Troubleshoot vSAN and HA Interoperability

To enable both Virtual SAN and vSphere HA on a cluster, Virtual SAN must be enabled first, followed by vSphere HA. You cannot enable Virtual SAN if vSphere HA is already enabled. To disable Virtual SAN on a cluster with vSphere HA also enabled, one must first of all disable vSphere HA. Only then can Virtual SAN be disabled.

Changing the vSphere HA Network – if both vSAN and HA are enabled on a cluster and the HA network changes, manual HA re-configuation is required to teach the hosts about the change.

Resolve vMotion and Storage vMotion Issues

Storage DRS is Disabled on a Virtual Disk – When the datastore cluster has Storage DRS enabled but some VMDK’s in the cluster have Storage DRS disabled.

Reasons for SDRS to be disabled on a virtual disk:

• VM’s swap file is specifically specified for the VM.
• VM’s .vmx file
• Storage vMotion is disabled
• The main disk of the VM is protected by HA and relocating will cause loss of HA protection
• The disk is a CD/ISO file
• If the disk is independant
• VM has system files on separate datastores.
• VM has a hidden disk. Such as snapshots
• VM is a template
• VM has Fault tolerance enabled
• VM is sharing files between disks

Datastore Can’t Enter Maintenance Mode

One or more disks can’t be migrated with Storage vMotion.

• Storage vMotion is disabled on a disk
• Storage vMotion rules are preventing Storage DRS from making migrations

How to fix?

• If SDRS is disabled, enable it and figure out why it’s disabled.
• Remove or disable any rules that are preventing SDRS from happening.
• Set the SDRS advanced option IgnoreAffinityRulesForMaintenance to 1.

Storage DRS Cannot Operate on a Datastore

• Datastore is shared across multiple datacenters
• Datastore is connect to an unsupported host
• Datastore is connected to a host that is not running Storage I/O Control

How to fix?

• Datastore must be visiable in only one datacenter
• Verify all hosts connected to the datastore cluster are running ESXi 5.0+
• Verify all host connected to the datastore cluster have Storage I/O Control enabled.

Storage DRS Generates Faults During VM Creation

• Review or remove any rule violations and retry the creation of the VM.

Applying Storage DRS Recommendations Fail

• The Thin Provisioning Threshold Crossed alarm is triggered for target datastore, which means the datastore is running out of space.
• Target datastore might be in maintenance mode

How to fix?

• Recify the issue that caused the Thin Provisioning Threshold alarm
• Remove target datastore from maintenance mode

Troubleshoot VMware Fault Tolerance

Hardware Virtualization Not Enabled

• Enable it in the BIOS of the host (if compatible)

Compatible Hosts  Not Available for Secondary VM

• Add more hosts to the cluster
• Verify hosts aren’t in maintenance mode
• Verify available resources including disk space
• Verify HV is enabled on all the hosts in the cluster

Secondary VM causing poor performance on Primary VM

• Verify the second VM isn’t running on an over-committed host
• Change the secondary VM’s datastore if disk contention is the issue
• Move the second VM to another host
• Apply resource limits on other VM OR investigate other VM’s on host running secondary VM.

Increased Network Latency Observed in FT VM’s

• Verify there is sufficient bandwidth between hosts.
• Verify the network link is functioning optimally.

Some Hosts are Overloaded with FT VM’s

DRS does not load balance Fault Tolerance enabled VM’s unless they are running in legacy mode.

• Manually move FT VM’s to redistribute the workload across other hosts.

Turning on FT for Powered-On VM’s Fail

• Check to see if there’s available memory to perform the operation.
• Move the VM to a host that has available resources.

FT VM’s not Placed or Evacuated by DRS

• Check the VM(s) for a VM override that is disabled DRS.