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Table Of Contents
Cause
When EVC is disabled on a DRS cluster, a VM override that disables DRS on an FT VM might be added.
Even if EVC is later reenabled, this override is not canceled.
Solution
If DRS does not place or evacuate FT VMs in the cluster, check the VMs for a VM override that is disabling
DRS. If you find one, remove the override that is disabling DRS.
NOTE For more information on how to edit or delete VM overrides, see vSphere Resource Management.
Fault Tolerant Virtual Machine Failovers
A Primary or Secondary VM can fail over even though its ESXi host has not crashed. In such cases, virtual
machine execution is not interrupted, but redundancy is temporarily lost. To avoid this type of failover, be
aware of some of the situations when it can occur and take steps to avoid them.
Partial Hardware Failure Related to Storage
This problem can arise when access to storage is slow or down for one of the hosts. When this occurs there
are many storage errors listed in the VMkernel log. To resolve this problem you must address your storage-
related problems.
Partial Hardware Failure Related to Network
If the logging NIC is not functioning or connections to other hosts through that NIC are down, this can
trigger a fault tolerant virtual machine to be failed over so that redundancy can be reestablished. To avoid
this problem, dedicate a separate NIC each for vMotion and FT logging traffic and perform vMotion
migrations only when the virtual machines are less active.
Insufficient Bandwidth on the Logging NIC Network
This can happen because of too many fault tolerant virtual machines being on a host. To resolve this
problem, more broadly distribute pairs of fault tolerant virtual machines across different hosts.
Use a10-Gbit logging network for FT and verify that the network is low latency.
vMotion Failures Due to Virtual Machine Activity Level
If the vMotion migration of a fault tolerant virtual machine fails, the virtual machine might need to be failed
over. Usually, this occurs when the virtual machine is too active for the migration to be completed with only
minimal disruption to the activity. To avoid this problem, perform vMotion migrations only when the
virtual machines are less active.
Too Much Activity on VMFS Volume Can Lead to Virtual Machine Failovers
When a number of file system locking operations, virtual machine power ons, power offs, or vMotion
migrations occur on a single VMFS volume, this can trigger fault tolerant virtual machines to be failed over.
A symptom that this might be occurring is receiving many warnings about SCSI reservations in the
VMkernel log. To resolve this problem, reduce the number of file system operations or ensure that the fault
tolerant virtual machine is on a VMFS volume that does not have an abundance of other virtual machines
that are regularly being powered on, powered off, or migrated using vMotion.
Lack of File System Space Prevents Secondary VM Startup
Check whether or not your /(root) or /vmfs/datasource file systems have available space. These file systems
can become full for many reasons, and a lack of space might prevent you from being able to start a new
Secondary VM.
Chapter 2 Troubleshooting Virtual Machines
VMware, Inc. 17