About allocation rules

The platform uses allocation rules to control the scheduling of resources in private cloud datacenters, to deploy your VMs to the desired hosts. Your virtualization technology must manage the use of resources in the virtualization technology.

For details of the allocation process, see the Virtual machine allocation section. 

There are two types of allocation rules: Global rules apply to all datacenters and Datacenter rules apply to the selected datacenter. 

You can manage Allocation rules on the datacenter Allocation rules tab.

For details of Allocation limits, see Control resource usage with allocation limits

Global load balance rules and datacenter load balance rules

For You can create the following types of load balance rules:

• PERFORMANCE:  select the physical machine with the most available resources. If more than one physical machine has the same resources available, use a round-robin algorithm to allocate each VM to a different physical machine.

• PROGRESSIVE:  select the same physical machine until it is full, then change to another one. Begin with the machine with the most available resources. Default rule

A datacenter load balance rule will have priority over a global load balance rule.

Privileges: Access infrastructure view and Private DCs, View datacenter details, Manage allocation rules

Load level compute rules

To specify the CPU and RAM load on machines, use compute load level rules. The scheduler will use these rules to help determine if a physical machine is a candidate to hold a VM. 

You can create load level rules for the following elements:

• a datacenter (all racks)

• a rack (all servers on the selected rack)

• a cluster (for supported hypervisors)

• a specific server 

You can only add one rule for an element at each level, but more than one rule may apply.

The priority order of rules is any cluster rule first (if it is present), then the other rules from the most specific rule to the least specific rule. A cluster rule affects all hosts in a cluster irrespective of their state, for example, it applies to hosts that are powered off.

An aggregate rule will apply to the sum of all resources in a group (datacenters, racks, or clusters). This means that the platform will sum all of the resources in the group and calculate the load level percentage of the total in order to determine the available resources for the group.

If you are using a cluster as a physical machine, to create rules for the cluster, select the Server option

Load level storage rules

To specify the storage load on machine datastores, use storage load level rules. The scheduler will use these rules to help determine if a physical machine is a candidate to hold a VM. 

You can create rules for the following elements:

• A datacenter (all datastore tiers)

• A tier (all datastores in a tier)

• A specific datastore.

If there is more than one rule that applies to a datastore, the most specific rule takes precedence over more general rules.

Restrict tenants from sharing servers

If a tenant does not want to deploy on the same physical machine as another tenant, use enterprise exclusion rules, which are called Restrict shared server rules. There is no limit on the amount of these rules you can create.

Note that you can also restrict servers by editing an enterprise in Users view. 

Redirect deployments with allocation rules

You can use allocation rules to redirect deployments. Here are some examples:

• To gradually migrate users to a new empty hypervisor, set load balance rules to performance. This will ensure that new deployments will go to the new machine. 

• To stop VMs from deploying to a specific physical machine, set load level rules to 1% for RAM and CPU. This will ensure that users cannot deploy more VMs to this physical machine. However, it is also important to consider that users will not be able to reconfigure the VMs that were already deployed there.

Manage allocation rules with the API

Related topics

• Manage enterprises#Configureenterpriseresources

• Manage enterprises#Reservephysicalmachinesandrestrictdeployments