vCenter Server supports a set of customization options, including monitoring, virtual machine fault tolerance, and so on.

VM and Application Monitoring Service

When enabled, the Virtual Machine and Application Monitoring service, which uses VMware Tools, evaluates whether each virtual machine in the cluster is running. The service checks for regular heartbeats and I/O activity from the VMware Tools process that is running on the guest OS. If the service receives no heartbeats or determines I/O activity, the guest operating system has likely failed or VMware Tools is not being allocated time for heartbeats or I/O activity. In this case, the service determines that the virtual machine has failed and reboots the virtual machine.

Enable VM Monitoring for automatic restart of a failed virtual machine. The application or service running on the virtual machine must be capable of restarting successfully after a reboot or the virtual machine restart is not sufficient.

Table 1. Design Decisions on Monitoring and Startup Order Configuration for Virtual Machines

Decision ID

Design Decision

Design Justification

Design Implication

ROBO-VI-VC-017

Enable VM Monitoring.

VM Monitoring provides in-guest protection for most VM workloads.

None.

VMware vSphere Distributed Resource Scheduling (DRS)

vSphere Distributed Resource Scheduling provides load balancing of a cluster by migrating workloads from heavily loaded ESXi hosts to less utilized ESXi hosts in the cluster. vSphere DRS supports manual and automatic modes.

Manual

Recommendations are made but an administrator needs to confirm the changes.

Automatic

Automatic management can be set to five different levels. At the lowest setting, workloads are placed automatically at power-on and only migrated to fulfill certain criteria, such as entering maintenance mode. At the highest level, any migration that would provide a slight improvement in balancing is performed.

Table 2. Design Decisions on vSphere DRS

Decision ID

Design Decision

Design Justification

Design Implication

ROBO-VI-VC-018

Enable vSphere DRS on all clusters and set it to Fully Automated, with the default setting (medium).

Provides the best trade-off between load balancing and excessive migration with vSphere vMotion events.

If a vCenter Server outage occurs, mapping from virtual machines to ESXi hosts might be more difficult to determine.

Enhanced vMotion Compatibility (EVC)

EVC works by masking certain features of newer CPUs to allow migration between ESXi hosts containing older CPUs. EVC works only with CPUs from the same manufacturer and there are limits to the version difference gaps between the CPU families.

If you set EVC during cluster creation, you can add ESXi hosts with newer CPUs at a later date without disruption. You can use EVC for a rolling upgrade of all hardware with zero downtime.

Set the cluster EVC mode to the highest available baseline that is supported for the lowest CPU architecture on the hosts in the cluster.

Table 3. Design Decisions on VMware Enhanced vMotion Compatibility

Decision ID

Design Decision

Design Justification

Design Implication

ROBO-VI-VC-019

Enable Enhanced vMotion Compatibility (EVC). Set the cluster EVC mode to the highest available baseline that is supported for the lowest CPU architecture on the hosts in the cluster.

Supports cluster upgrades without virtual machine downtime.

You can enable EVC only if clusters contain hosts with CPUs from the same vendor.