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
3 Calculates the Current CPU Failover Capacity and Current Memory Failover Capacity for the cluster.
4 Determines if either the Current CPU Failover Capacity or Current Memory Failover Capacity is less
than the corresponding Congured Failover Capacity (provided by the user).
If so, admission control disallows the operation.
vSphere HA uses the actual reservations of the virtual machines. If a virtual machine does not have
reservations, meaning that the reservation is 0, a default of 0MB memory and 32MHz CPU is applied.
N The cluster resources percentage option for admission control also checks that there are at least two
vSphere HA-enabled hosts in the cluster (excluding hosts that are entering maintenance mode). If there is
only one vSphere HA-enabled host, an operation is not allowed, even if there is a sucient percentage of
resources available. The reason for this extra check is that vSphere HA cannot perform failover if there is
only a single host in the cluster.
Computing the Current Failover Capacity
The total resource requirements for the powered-on virtual machines is comprised of two components, CPU
and memory. vSphere HA calculates these values.
n
The CPU component by summing the CPU reservations of the powered-on virtual machines. If you
have not specied a CPU reservation for a virtual machine, it is assigned a default value of 32MHz (this
value can be changed using the das.vmcpuminmhz advanced option.)
n
The memory component by summing the memory reservation (plus memory overhead) of each
powered-on virtual machine.
The total host resources available for virtual machines is calculated by adding the hosts' CPU and memory
resources. These amounts are those contained in the host's root resource pool, not the total physical
resources of the host. Resources being used for virtualization purposes are not included. Only hosts that are
connected, not in maintenance mode, and have no vSphere HA errors are considered.
The Current CPU Failover Capacity is computed by subtracting the total CPU resource requirements from
the total host CPU resources and dividing the result by the total host CPU resources. The Current Memory
Failover Capacity is calculated similarly.
Example: Admission Control Using Cluster Resources Percentage
The way that Current Failover Capacity is calculated and used with this admission control policy is shown
with an example. Make the following assumptions about a cluster:
n
The cluster is comprised of three hosts, each with a dierent amount of available CPU and memory
resources. The rst 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 ve powered-on virtual machines in the cluster with diering 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 Congured Failover Capacity for CPU and Memory are both set to 25%.
vSphere Availability
20 VMware, Inc.