Flexible resource allocation is a built-in vCMP^® feature that allows vCMP host administrators to optimize the use of available system resources. Flexible resource allocation gives you the ability to configure the vCMP host to allocate a different amount of CPU and memory to each guest, based on the needs of the specific BIG-IP^® modules provisioned within a guest. When you create each guest, you specify the number of cores that you want the host to allocate to the guest. Configuring these settings determines the total amount of CPU and memory that the host allocates to the guest. With flexible allocation, you can customize CPU and memory allocation in granular ways that meet the specific resource needs of each individual guest.

Before you create vCMP^® guests and allocate system resources to them, you need to determine the specific CPU and memory needs of each guest. You can then decide how many cores to allocate to a guest, factoring in the resource capacity of your hardware platform.

To determine the CPU and memory resource needs, you must know:

• The number of guests you need to create
• The specific BIG-IP^® modules you need to provision within each guest
• The combined memory requirement of all BIG-IP modules within each guest

When you create a vCMP^® guest, you must decide on the amount of dedicated CPU and memory that you want the vCMP host to allocate to the guest.

To manage network throughput for a vCMP^® guest, you should understand the throughput capacity of your appliance model, as well as the throughput limit you want to apply to each guest:

Throughput capacity

Each appliance model has a total throughput capacity, which defines the combined upper limit on throughput for guests.

Throughput limits per guest

Throughput requirements for a guest are typically lower than the throughput capacity of the appliance on which the guest runs. Consequently, you can define a specific network throughput limit for each guest. When vCMP is provisioned on the system, you define a guest's throughput limit by logging in to the vCMP host and creating a rate shaping object known as a Single Rate Three Color Marker (srTCM) Policer. You then assign the policer to one or more guests when you create or modify the guests. It is important that the srTCM values that you assign to a guest do not exceed the combined throughput capacity of the appliance model.

As a vCMP^® host administrator, you can control when the system allocates or de-allocates system resources to a guest. You can do this at any time, by setting a guest to one of three states: Configured, Provisioned, or Deployed. These states affect resource allocation in these ways:

Configured

This is the initial (and default) state for newly-created guests. In this state, the guest is not running, and no resources are allocated to the guest. If you change a guest from another state to the Configured state, the vCMP host does not delete any virtual disks that were previously attached to that guest; instead, the guest's virtual disks persist on the system. The host does, however, automatically de-allocate other resources such as CPU and memory. When the guest is in the Configured state, you cannot configure the BIG-IP^® modules that are licensed to run within the guest; instead, you must set the guest to the Deployed state to provision and configure the BIG-IP modules within the guest.

Provisioned

When you change a guest from Configured to Provisioned, the vCMP host allocates system resources to the guest (CPU, memory, and any unallocated virtual disks). If the guest is new, the host creates new virtual disks for the guest and installs the selected ISO image on them. A guest does not run while in the Provisioned state. When you change a guest from Deployed to Provisioned, the host shuts down the guest but retains its current resource allocation.

Deployed

When you change a guest to the Deployed state, the guest administrator can then provision and configure the BIG-IP modules within the guest. If you are a host administrator and you reconfigure the properties of a guest after its initial deployment, the host immediately propagates those changes to all of the guests and also propagates the list of allowed VLANs.

Normally when sharing SSL resources, if all guests are using similar-sized keys, each guest receives an equal share of the SSL resource. Also, if any guests are not using SSL keys, then other guests can take advantage of the extra SSL resource.

The exception is platforms containing high-performance SSL processors. These platforms allocate SSL resource according to an SSL mode that you configure for each guest when you create it. The available modes are: Shared, Dedicated, and None.

When creating vCMP guests, you cannot create both Dedicated- and Shared-mode guests on the same system. That is, if you configure a guest for Dedicated mode, any other guest you create must be in either Dedicated or None mode. The number of guests that can be in Dedicated mode equals the number of SSL processors that your hardware platform provides.

The same applies to configuring a guest for Shared mode; if you configure a guest for this mode, any other guest must be in either Shared or None mode.

For more information on the SSL Mode setting for a guest, see the section titled vCMP host administrator tasks that describes how to create a vCMP guest.