Pre-caching

Pre-caching lets you preload the Content Distribution caches of particular machines directly from the Configuration Manager console. This enables downloads to be available on the branch prior to a deployment taking place, which can be very useful in large-scale deployment scenarios.

Before you start, ensure the following prerequisites are met:

• 1E Platform is accessible, with Content Distribution features enabled.

• Content Distribution Configuration Manager console extensions must be installed.

Refer to Using Nomad with Operating System Deployment OSD for example scenarios about how to use Content Distribution to maximize the efficiency of distributing large OS content across the network and how you can monitor those deployments using the Content Distribution app.

Architecture and ports

Pre-caching uses the following ports in its communications. If a site server is configured to use custom ports, pre-caching will use those ports to communicate with a management or distribution points. To ensure high-availability, pre-caching falls back to next available site server if it fails to communicate with a management or distribution point.

Enabling pre-caching

When you consider how to install the Nomad Branch Tools (refer to Installing 1E Content Distribution Tools), you can also install them in unattended mode by using the MODULE.NOMAD.PLATFORMURL installer property or by setting the PlatformURL registry value on the machine where the extensions are installed post-installation.

Content Distribution clients must also be configured to support pre-caching. This is done during installation in the Content Distribution screen of the 1E Client installer, for more details refer to Content Distribution client.

Using pre-caching

Pre-caching is directly integrated with the Configuration Manager Console, is fully compliant and works with Role Based Access in Configuration Manager, refer to Pre-caching RBAC support.

To start the pre-cache wizard, right-click any of the following types of content in the Configuration Manger console and from the context menu, choose Pre-cache content using Nomad.

• Applications

• Packages

• Driver packages

• Operating system images

• Operating system upgrade packages

• Boot images

• Task sequences: Refer to the note in the table under Dynamic pre-caching

1. On the Targeting screen, choose the device collection you want to pre-cache.

   

2. On the Summary screen, verify your selection.

   • Click Apply if it is correct.

   • If it is incorrect, click Previous to start again.

3. The Progress screen displays the status while the wizard sets up the pre-cache notification in ContentDistribution.

   There is support for providing alternate credentials to authenticate with the 1E Platform. If your 1E Platform instance resides in another domain or the cloud, you will be prompted to enter alternate credentials for that location, which get stored in the credential store for any future requests.

   

4. On the Completion screen, click Finish to close the wizard.

   

Viewing pre-cached jobs

If you are not a full administrator, you can only view pre-cached jobs provided you have Read permissions on the collection as well as the content.

To view pre-cached jobs:

1. In Configuration Manager, choose Monitoring.

2. Expand the 1E Nomad node and select Pre-caching Jobs.

The attributes for the job are displayed in the right-hand pane as follows:

Deleting pre-cached jobs

You can only delete pre-cached jobs if you have permissions for a particular content type. If you are not a full administrator, you will need:

• Read permissions on collections (through a security role).

• Access to the pre-cached job (i.e. content and the device collection).

To delete a pre-cached job:

1. In Configuration Manager, choose Monitoring.

2. Expand the Overview tree and choose Nomad Pre-cache jobs.

3. In the Nomad Pre-cache jobs list, right-click the pre-cached you want and from the context menu, choose Delete.

Managing pre-cached jobs with Powershell cmdlets

You can also manage pre-cached jobs by using PowerShell cmdlets.

To get all pre-cached jobs from ContentDistribution, run:

Get-PreCachingJobs [-PlatformURL <String>] [<CommonParameters>]

To remove pre-cached jobs from ContentDistribution run:

Remove-PreCachingJobs [-Id] <String> [-PlatformURL <String>] [-Confirm [<SwitchParameter>]] [<CommonParameters>]

Remove-PreCachingJobs -Before <String> [-PlatformURL <String>] [-Confirm [<SwitchParameter>]] [<CommonParameters>]

Remove-PreCachingJobs -AgeInDays <UInt32> [-PlatformURL <String>] [-Confirm [<SwitchParameter>]] [<CommonParameters>]

Remove-PreCachingJobs -All [<SwitchParameter>] [-PlatformURL <String>] [-Confirm [<SwitchParameter>]] [<CommonParameters>]

The parameters are:

There is more information about CommonParameters at about_CommonParameters.

Dynamic pre-caching

If the content or membership of a targeted collection changes after a pre-cached job is created, Content Distribution is updated to keep in sync with Configuration Manager. It does this by polling the Configuration Manager database at regular intervals to fetch updated content.

Each synchronization task fetches the following:

• Pre-caching data (device collections and contents)

• Dashboard data (status messages)

Pre-cached jobs are affected when these events take place in Configuration Manager, and on the next synchronization with Content Distribution:

Hash validation

Hash validation is used when content is downloaded for pre-cached jobs and for LSZgen requests for these jobs. When a pre-cached job is created:

• For task sequences, hashes for all referenced packages and applications are posted to Content Distribution.

• For applications, hashes for all its child deployment types are posted to Content Distribution.

On the client side:

• Where a job is queued, the client queries the management point for content locations. The management point returns a hash for application content types only. If it does not return a hash, the client retrieves it from Content Distribution. Hashes from management points take priority over Content Distribution.

• For the 1E server hosting Content Distribution, the client fetches the hash during the pre-cache cycle for that particular content.

Content Distribution clients polling the ContentDistribution database

After running the wizard, Content Distribution clients that are registered with the ContentDistribution database, and that were included in the selected device collection, will get a pre-cache notification within 24 hours. This notification tells Content Distribution that it has to process a download job on the content to be cached. The default number of notifications a client processes in one pre-cache poll cycle is 20, but you can modify this by updating the PrecachePollBatchSize registry value.

When is polling disabled?

Content Distribution clients normally start their polling cycle when the service starts, with a random delay to minimize the possibility of multiple simultaneous polls from different clients. However, polling will not start if any of the following is true:

1. The 1E Platform URL is not set in the Content Distribution registry.

2. Content Distribution is running on a machine using the Win PE operating system.

3. The Configuration Manager client is not installed on the machine – in order to download pre-cached content, the Content Distribution service needs to contact the management point and this is only possible if the client is installed locally.

To explicitly turn polling off for a Content Distribution client set the PrecachePollMinutes registry value to 0.

Pre-caching RBAC support

Pre-caching is tightly integrated into Configuration Manager and honors the permissions and restrictions enforced by role-based access control (RBAC). The following rules are used to determine whether a particular user is allowed to pre-cache a particular content on a particular collection or not:

1. A user is only allowed to pre-cache a content item if they have the RBAC permissions to deploy it via Configuration Manager.

2. A user is only allowed to pre-cache to a device collection if they have the RBAC permissions to access that collection.

Configuration Manager administrators will need to be a member of the Content Distribution Administrators group, so they can manage Configuration Manager collections, for example create, view and delete pre-cache and paused collections. Refer to Roles and permissions for details.

If an administrator does not have the necessary RBAC permissions, they will not be able to see or access any of the pre-cache features in the Configuration Manager Admin console. Similarly, if they do not have the right permissions to a device collection, that collection will not be available to them in the Targeting screen of the pre-cache wizard.

However, full administrators will see:

The following table provides an overview of the availability of pre-caching for the built-in Configuration Manager security roles.

Limitations

The following limitations are part of the current implementation of the pre-caching feature:

1. Software Updates are not supported by pre-caching. Instead, make use of the available and mandatory advertisement dates.

2. Disabling Content Distribution Content Registration with the ContentDistribution database prevents clients from fetching further pre-caching notifications after the first batch of 20.

3. The pre-caching Wizard allows packages that do not have content to be selected for pre-caching.

4. Delays may be seen when processing pre-caching notifications for devices with many notifications. By default, clients will poll the ContentDistribution database once a day. Each time a client polls it will fetch a batch of 20 notifications to process, so for a client with 100 outstanding pre-caching notifications, it will take 5 days for all the notifications to be processed. The time between polls depends on the PrecachePollMinutes setting which can be reduced if there are many pre-caching jobs, though the 24-hour default is recommended.

5. Pre-caching jobs do not support Content Distribution additional settings (such as those configurable in the Nomad tab in the Package or Task Sequence properties).

6. Content Distribution won't re-download a pre-caching job with updated data format (that is compressed/encrypted), if the content has previously downloaded to the cache. The conversion will happen when ACP triggers the same content.

7. Content Distribution synchronization may cause issues if there is any replication issues between the central administration site and primary site.

8. Workgroup member clients may not be able to use the pre-caching feature, as it requires ContentDistribution registration using their FQDN.

Using network access accounts

Prior to this release, when a download is initiated, Content Distribution only used the credentials from the first Configuration Manager network access account it found to authenticate, and if that failed, the download stopped. From this release, Content Distribution cycles through all native Configuration Manager network access accounts to authenticate, thereby reducing the risk of failure.