Chapter 16. Quotas and Service Level Agreement Policy

Quota is a resource limitation tool provided with Red Hat Virtualization. Quota may be thought of as a layer of limitations on top of the layer of limitations set by User Permissions.

Quota is a data center object.

Quota allows administrators of Red Hat Virtualization environments to limit user access to memory, CPU, and storage. Quota defines the memory resources and storage resources an administrator can assign users. As a result users may draw on only the resources assigned to them. When the quota resources are exhausted, Red Hat Virtualization does not permit further user actions.

There are two different kinds of Quota:

Quota, like SELinux, has three modes:

When a user attempts to run a virtual machine, the specifications of the virtual machine are compared to the storage allowance and the runtime allowance set in the applicable quota.

If starting a virtual machine causes the aggregated resources of all running virtual machines covered by a quota to exceed the allowance defined in the quota, then the Manager refuses to run the virtual machine.

When a user creates a new disk, the requested disk size is added to the aggregated disk usage of all the other disks covered by the applicable quota. If the new disk takes the total aggregated disk usage above the amount allowed by the quota, disk creation fails.

Quota allows for resource sharing of the same hardware. It supports hard and soft thresholds. Administrators can use a quota to set thresholds on resources. These thresholds appear, from the user’s point of view, as 100% usage of that resource. To prevent failures when the customer unexpectedly exceeds this threshold, the interface supports a "grace" amount by which the threshold can be briefly exceeded. Exceeding the threshold results in a warning sent to the customer.