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
The Current Failover Capacity is computed by determining how many hosts (starting from the largest) can
fail and still leave enough slots to satisfy the requirements of all powered-on virtual machines.
Example: Admission Control Using Slot Policy
The way that slot size is calculated and used with this admission control policy is shown in an example.
Make the following assumptions about a cluster:
n
The cluster is comprised of three hosts, each with a different amount of available CPU and memory
resources. The first host (H1) has 9GHz of available CPU resources and 9GB of available memory,
while Host 2 (H2) has 9GHz and 6GB and Host 3 (H3) has 6GHz and 6GB.
n
There are five powered-on virtual machines in the cluster with differing CPU and memory
requirements. VM1 needs 2GHz of CPU resources and 1GB of memory, while VM2 needs 2GHz and
1GB, VM3 needs 1GHz and 2GB, VM4 needs 1GHz and 1GB, and VM5 needs 1GHz and 1GB.
n
The Host Failures Cluster Tolerates is set to one.
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.
vSphere Availability
VMware, Inc. 25