6.7
Table Of Contents
- vSphere Availability
- Contents
- About vSphere Availability
- Business Continuity and Minimizing Downtime
- Creating and Using vSphere HA Clusters
- Providing Fault Tolerance for Virtual Machines
- How Fault Tolerance Works
- Fault Tolerance Use Cases
- Fault Tolerance Requirements, Limits, and Licensing
- Fault Tolerance Interoperability
- Preparing Your Cluster and Hosts for Fault Tolerance
- Using Fault Tolerance
- Best Practices for Fault Tolerance
- Legacy Fault Tolerance
- Troubleshooting Fault Tolerant Virtual Machines
- Hardware Virtualization Not Enabled
- Compatible Hosts Not Available for Secondary VM
- Secondary VM on Overcommitted Host Degrades Performance of Primary VM
- Increased Network Latency Observed in FT Virtual Machines
- Some Hosts Are Overloaded with FT Virtual Machines
- Losing Access to FT Metadata Datastore
- Turning On vSphere FT for Powered-On VM Fails
- FT Virtual Machines not Placed or Evacuated by vSphere DRS
- Fault Tolerant Virtual Machine Failovers
- vCenter High Availability
- Plan the vCenter HA Deployment
- Configure the Network
- Configure vCenter HA With the Basic Option
- Configure vCenter HA With the Advanced Option
- Manage the vCenter HA Configuration
- Set Up SNMP Traps
- Set Up Your Environment to Use Custom Certificates
- Manage vCenter HA SSH Keys
- Initiate a vCenter HA Failover
- Edit the vCenter HA Cluster Configuration
- Perform Backup and Restore Operations
- Remove a vCenter HA Configuration
- Reboot All vCenter HA Nodes
- Change the Appliance Environment
- Collecting Support Bundles for a vCenter HA Node
- Troubleshoot Your vCenter HA Environment
- Patching a vCenter High Availability Environment
- Using Microsoft Clustering Service for vCenter Server on Windows High Availability
Figure 2‑1. Admission Control Example with Percentage of Cluster Resources Reserved
Policy
total resource requirements
7GHz, 6GB
total host resources
24GHz, 21GB
2GHz
1GB
2GHz
1GB
1GHz
2GB
1GHz
1GB
1GHz
1GB
VM1
9GHz
9GB
H1
9GHz
6GB
H2
6GHz
6GB
H3
VM2 VM3 VM4 VM5
The total resource requirements for the powered-on virtual machines is 7GHz and 6GB. The total host
resources available for virtual machines is 24GHz and 21GB. Based on this, the Current CPU Failover
Capacity is 70% ((24GHz - 7GHz)/24GHz). Similarly, the Current Memory Failover Capacity is 71%
((21GB-6GB)/21GB).
Because the cluster's Configured Failover Capacity is set to 25%, 45% of the cluster's total CPU
resources and 46% of the cluster's memory resources are still available to power on additional virtual
machines.
Slot Policy Admission Control
With the slot policy option, vSphere HA admission control ensures that a specified number of hosts can
fail and sufficient resources remain in the cluster to fail over all the virtual machines from those hosts.
Using the slot policy, vSphere HA performs admission control in the following way:
1 Calculates the slot size.
A slot is a logical representation of memory and CPU resources. By default, it is sized to satisfy the
requirements for any powered-on virtual machine in the cluster.
2 Determines how many slots each host in the cluster can hold.
3 Determines the Current Failover Capacity of the cluster.
This is the number of hosts that can fail and still leave enough slots to satisfy all of the powered-on
virtual machines.
vSphere Availability
VMware, Inc. 23