Connector configurations

The first time you use the App Layering service, you need to add at least one connector configuration to use for creating layers and publishing layered images.

A connector is an interface for giving the App Layering appliance access to locations in your virtual infrastructure.

A connector configuration is a stored set of credentials for a location on your hypervisor or provisioning service. When creating layers or publishing images, you select one for the appliance to use for these operations.

Why use connector configurations

Connector configurations let the App Layering appliance access locations in your environment for creating layers or publishing layered images. Selecting a connector configuration automates the file transfer process and saves time.

You can use a connector configuration to:

  • Import an OS image into a new layer.
  • Create app and platform layers or add versions to an OS layer. You can also select a script to run.
  • Publish layered images to your hypervisor or provisioning service, or run a script. For example, you can select a script to run when an image is launched.

Import your OS image into an OS layer

When you create an OS layer, you need a connector configuration to give the appliance access to the location of the OS image.

Create layers

To speed up layer creation, you need a connector configuration with the credentials for the hypervisor location where you plan to install the software for a layer. This connector configuration includes a Packaging Cache option, which is enabled by default to afford you the best layering performance.

Publish layered images

You need a connector configuration for each location to which you are publishing layered images. Once published, you use layered images to provision systems for specific groups of users.


To create a connector configuration, you need to meet the following requirements.


Valid account credentials that the appliance can use to access a location in your environment. For details about the values you need, select the hypervisor or provisioning service later in this section.

Disk space for cache

On all supported hypervisors, except for Azure, the default Packaging cache size is set to the recommended starting level. Allow enough disk space to increase the cache size, if needed.

About offloading compositing (Hyper-V, VMware vSphere only)

When creating a layer or publishing a layered image, you can dramatically increase performance by selecting a connector configuration with Offload Compositing enabled.

Besides improving performance, Offload Compositing lets you:

  • Create the layer or image as a UEFI, Generation 2 machine.
  • Use the VHDX disk format for either BIOS, Generation 1 or UEFI, Generation 2 images.

Packaging a layer

When using Offload Compositing in the connector configuration, packaging a layer begins as soon as you shut down the machine for finalization. The packaging is done automatically. You do not have to manually select Finalize in the management console.


In this release, you cannot use Offload Compositing when creating an OS layer from scratch, but you can add a version to the layer with Offload Compositing selected.

As long as Offload Compositing is selected, you can make the new layer version UEFI, Generation 2 and you can select VHDX disk format. VHDX format is supported on both BIOS, Generation 1 and UEFI, Generation 2 machines, as long as you are using Offload Compositing.

Publishing an image

When you publish an image, the publishing machine builds the image on the hypervisor (Hyper-V, VMware vSphere) server.

About Packaging cache size and hit rate

Connector configurations for all hypervisors except Azure let you configure space for a Packaging cache. The appliance uses this cache on your hypervisor to speed up layer packaging.

Packaging cache size

We recommend using packaging cache at the default starting size for your hypervisor:

  • vSphere: 250GB
  • Citrix Hypervisor (formerly XenServer): 480GB
  • Hyper-V: 200GB
  • Nutanix: 480GB

As unique App layers are created, you may need to increase the Packaging cache size. The more App layers, the bigger the cache required.

Hit rate

The hit rate is the percentage of times the appliance has found a disk in the cache. A low hit rate means the cache is not offering much benefit, because there is not enough space for the number of disks you have.

If you have a low hit rate, you should improve it by increasing the Packaging cache size, as described below. Increasing the cache size allows more disks to be stored in the cache. It also increases the likelihood of finding a disk needed for packaging in the cache. This results in a higher hit rate.

View connector configurations

The System > Connectors tab lists the connector configurations that you have created.

Image of the Connectors tab

Sort connector configurations

By default, connector configurations are listed in alphabetical order by name. You can also sort them by platform.

View connector configuration details

When caching is enabled for a connector configuration, the Connectors tab displays the cache size for that configuration.

Image of the cache size option

To see the values for any given connector configuration:

  1. Click the info icon to the left of the name. Details about the connector configuration are displayed.

View Cache size and Hit rate

The Packaging Cache Size and Hit rate are displayed when the Packaging Cache Size is set to a value greater than zero (0).

Add a connector configuration

This section explains how to add a connector configuration using the System > Connectors tab, which is where you manage your configurations.

If when creating a layer or image template you don’t find the connector configuration you need, you can also add a new one by selecting New on the wizard’s Connector tab. From there you can use the detailed steps below.

To add a connector configuration, follow these steps:

  1. Access the management console, and select System > Connectors. This is where connector configurations are listed.
  2. Click Add Connector Config in the Action bar. This opens a dialog box where you can select the type of connector configuration to create.
  3. Choose the connector type from the drop-down menu.
  4. Complete the fields on the connector configuration page.
  5. Click the Test button to verify that the connector can access the location specified using the credentials supplied.
  6. Click Save. The new connector configuration appears on the Connector tab.

Image of the connector configuration

Edit a connector configuration

To edit a connector configuration:

  1. Access the management console, and select System > Connectors.
  2. Select the connector and click Edit Connector Config on the action panel. The connector configuration is displayed.
  3. Update the configuration, as needed.
  4. Click the Test button to verify that the connector can access the location specified using the credentials supplied.
  5. Click Save. The connector configuration is updated.

Increase the Cache size and Hit rate

To improve the utility of the cache and therefore increase the hit rate by editing the Packaging Cache Size:

  1. Select the connector and click Edit Connector Config on the action panel.
  2. Scroll to Layer Disk Cache Size in GB and enter the amount of space that the cache can occupy.
  3. Click the Test button to verify that the connector can access the location specified by using the credentials supplied.
  4. Click Save. The connector configuration is updated.

Continue adjusting the cache size until you achieve the layering performance you are looking for.

Disable or re-enable caching

Caching is now enabled and set to a recommended starting size by default, and we strongly recommend that you use it. If you decide to disable caching for a connector configuration, set the cache size to zero (0). If you need to re-enable it, simply increase the Packaging cache size.

Delete a connector configuration

If a connector configuration is deleted by another user while you are working in the Connectors tab, it may take a few minutes for the connector configuration to disappear from the list.

To delete a connector configuration:

  1. In the management console, select System > Connectors.
  2. Make sure that the connector configuration is not in use.
  3. Click Delete Connector Config on the Action bar.
  4. In the pop-up window that opens, select Yes. The connector configuration is deleted.

Messages you may receive when deleting configurations

If a connector configuration is in use when you attempt to delete it, you receive a message similar to the following example.


Validation Error: Unable to delete connector configuration ‘Citrix Provisioning - ConnectorExample’ as it is in use. If you receive this error message, remove the connector configuration from the layer or image template where it is still in use. Then delete the configuration.