Microsoft Windows 7 Security Update May Cause Performance Change For MSI Installations

Microsoft Windows 7 Security Update May Cause Performance Change For MSI Installations

Summary

Information on OS update that may change performance of MSI installation

Synopsis

There is a Microsoft Security Update available on Windows 7 machines, KB3072630, which can cause a change in behavior for MSI installations.

This change does not affect the installation itself, meaning your installation will still work as expected even after this security update is applied. However after this security update is applied, the Windows Installer service seems to read/scan files within your installation package in a different way. This difference can show up in certain cases and you may see an increase in the amount of time it takes for your installation\data transfer to complete.

Discussion

While the specifics of the changes to the Windows Installer service are not fully known, this change in behavior can be observed in the following example.

Say you have an example MSI installation package that includes features 'FeatureA' and 'FeatureB', each with a large number of unique components associated with them. If you were to then install this installation on a Windows 7 machine, prior to the security update being installed, if you only selected 'FeatureA', then the Windows Installer service will only read/scan the components related to 'FeatureA'.
However after installing the security update, if you repeat the same install and only select 'FeatureA' again, this time the Windows Installer service will read/scan all components in the setup (...meaning components associated to both 'FeatureA' and 'FeatureB'). While only the components from 'FeatureA' are installed on the system, this difference in the Windows Installer engine has been observed.

NOTE: You can make sure of a tool like Process Monitor to see what the Windows Installer service is accessing.

In most cases, this change in behavior is not noticable. However if you are distributing a large MSI installation on a DVD media and you happen to only want to install feature with a small number of files, this change may become noticable. While the installation of this single feature will still work as expected, the time needed to complete the data transfer may increase.

Workaround

While the KB3072630 article for the above Microsoft Security Update mentions that a temporary undo of the security fix can be applied to the OS. While this will work for the issue described in the security update, this workaround does not change the behavior of the Windows Installer service.
Furthermore it appears that this behavior is by design so there is no way to workaround this.
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‎Jul 12, 2018 09:53 PM
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