6.5.1
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
- 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
- Index
Figure 2‑2. Admission Control Example with Host Failures Cluster Tolerates Policy
6 slots remaining
if H1 fails
slot size
2GHz, 2GB
2GHz
1GB
2GHz
1GB
1GHz
2GB
1GHz
1GB
1GHz
1GB
VM1
9GHz
9GB
4 slots
H1
9GHz
6GB
3 slots
H2
6GHz
6GB
3 slots
H3
VM2 VM3 VM4 VM5
1 Slot size is calculated by comparing both the CPU and memory requirements of the virtual machines
and selecting the largest.
The largest CPU requirement (shared by VM1 and VM2) is 2GHz, while the largest memory
requirement (for VM3) is 2GB. Based on this, the slot size is 2GHz CPU and 2GB memory.
2 Maximum number of slots that each host can support is determined.
H1 can support four slots. H2 can support three slots (which is the smaller of 9GHz/2GHz and
6GB/2GB) and H3 can also support three slots.
3 Current Failover Capacity is computed.
The largest host is H1 and if it fails, six slots remain in the cluster, which is sucient for all ve of the
powered-on virtual machines. If both H1 and H2 fail, only three slots remain, which is insucient.
Therefore, the Current Failover Capacity is one.
The cluster has one available slot (the six slots on H2 and H3 minus the ve used slots).
Dedicated Failover Hosts Admission Control
You can congure vSphere HA to designate specic hosts as the failover hosts.
With dedicated failover hosts admission control, when a host fails, vSphere HA aempts to restart its virtual
machines on any of the specied failover hosts. If restarting the virtual machines is not possible, for example
the failover hosts have failed or have insucient resources, then vSphere HA aempts to restart those
virtual machines on other hosts in the cluster.
To ensure that spare capacity is available on a failover host, you are prevented from powering on virtual
machines or using vMotion to migrate virtual machines to a failover host. Also, DRS does not use a failover
host for load balancing.
N If you use dedicated failover hosts admission control and designate multiple failover hosts, DRS does
not aempt to enforce VM-VM anity rules for virtual machines that are running on failover hosts.
Chapter 2 Creating and Using vSphere HA Clusters
VMware, Inc. 23