When IIS uses the NAS share method to access a file, the IIS accesses the NAS many times. In contrast to the access to a local file system, each access to NAS involves at least one interaction over the network. Although each access lasts a short time, the client waits for a long time after many accesses of the IIS.
To improve the performance, see this article.
You can change the three registry keys mentioned in the article to a greater value, for example, 600 or greater.
The three registry keys are all at HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanWorkstation\Parameters. Their names are:
We recommend that you store JS files, CSS files, and other content related to webpage programs on your local storage, because the IIS accesses these files quite frequently.