Hey folks,

Kurt Falde, one of our Support Escalation Engineers, create this summary about the recent definition changes:

In the past month the AV definition team have released some much needed changes with regards to AV definition and how they are downloaded to WSUS servers during sync intervals. While the changes do not affect clients from a size perspective they do slightly affect which packages they will download and install during an update.

I’m not going to go into how it previously worked here but if you are interested read the previous 2 articles for some background info: http://blogs.technet.com/b/kfalde/archive/2009/02/09/understanding-fcs-definitions.aspx

http://blogs.technet.com/b/kfalde/archive/2009/03/05/wsus-fcs-definitions.aspx

Instead I’m going to try to detail out what a WSUS server currently downloads from MU on a monthly basis as well as the signature interval basis (every 8 hours).

Monthly:

• Complete Engine files for both x86 and x64 (6.67Mb and 5.34Mb for this past month)
• Binary Differencing files for the engine to bring it from last months to the current months engine for both x86 and x64 (.79Mb and .61Mb for this past month)
• Complete Definition base files for both x86 and x64 (50.7Mb and 50.7Mb for this past month)
• Binary Differencing files for bringing the definition base sets from last months to the current months for both x86 and x64 (5.18Mb and 5.18Mb for this past month)
• MpSigStub.exe the command line installer that actually installs the engine/signatures for both x86 and x64 (.21Mb and .26Mb for this past month)

Summarizing the sizes

Signature Release Interval (Every 8 hours)

• 3 sets of Binary Delta Definitions, each set has a BDD for both x86 and x64 covering a binary difference file from the last 3 release intervals to get definitions up to the currently released definition.  (from a recent set it was .34Mbx2 .50Mbx2 1.64Mbx2 for the various binary delta files these are usually about right as it gets larger they farther away you get from the current definition and thus binary patching isn’t as effective)
• 1 set of Delta Definitions, each set contains a Delta definition for both x86 and x64 to get signatures from the monthly base up to the currently released definition. (checking the Delta signatures from the past month the sizes ran from about .62Mb from the beginning of the rebase cycle up to around 4Mb right before rebasing again)

Summarizing the sizes

I want to stress here none of these file sizes are definitive.  Definition sizes in general for the base sets are always growing. The BDD sizes are usually fairly consistent as well as the engine file sizes.