Storing Update Files Locally or on Microsoft Update

You can store files locally on the WSUS server or on Microsoft Update. Storing update files locally on the WSUS server can potentially save bandwidth on your Internet connection because clients download updates directly from the WSUS server.

However, storing update files on Microsoft update saves disk space on the WSUS server and is useful if you have mobile clients, branch offices, or any scenario where a direct connection to the Internet exists and downloading updates over a WAN connection would introduce additional complexity.

To specify that you want to store update files on Microsoft Update and have clients download approved updates directly from Microsoft Update, set IUpdateServerConfiguration.HostBinariesOnMicrosoftUpdate to true.

If this property is set to false, WSUS stores the update files locally and clients download approved updates from the WSUS server. If HostBinariesOnMicrosoftUpdate is false, you must also specify values for the following settings:

• IUpdateServerConfiguration.DownloadExpressPackages
• IUpdateServerConfiguration.DownloadUpdateBinariesAsNeeded
• Select update languages using either IUpdateServerConfiguration.AllUpdateLanguagesEnabled or IUpdateServerConfiguration.SetEnabledUpdateLanguages

If HostBinariesOnMicrosoftUpdate is true, WSUS ignores DownloadExpressPackages and DownloadUpdateBinariesAsNeeded, and AllUpdateLanguagesEnabled must be set to true.

To reduce network bandwidth consumption and save disk space on the WSUS server, set IUpdateServerConfiguration.DownloadUpdateBinariesAsNeeded to true. This setting downloads only the metadata and license agreement for the updates when the WSUS server synchronizes with Microsoft Update. The update files themselves are downloaded only after you approve an update for installation.

To provide for a faster download and installation of the updates on client computers, set IUpdateServerConfiguration.DownloadExpressPackages to true. Using express packages is a good option if you are servicing clients over slow links with your WSUS server. Express installation update files contain binary differences that are merged with the current binary on the client. Express installation files can reduce the bandwidth consumed on your local network because only the binary difference is downloaded to the client and it is typically smaller than a full update file.

However, express installation files that you download to the WSUS server are typically larger than a full update file because an express installation file must contain all the binary differences for each revision that it is meant to update. This can increase the bandwidth consumption on your Internet connection (connection between WSUS and Microsoft Update).

Not all updates provide express installation files. If the update does not provide an express installation file, the full update file is downloaded.

For an example that sets these properties, see Specifying Updates to Synchronize.