A while back we extending our SharePoint 2010 server to provide an extranet enabling users to access SharePoint across the Internet. The main benefit being that users didn’t have to use VPN to access their content and data. The problem was that the extranet performance was too slow.
Part of the SharePoint extranet solution used ISA Server 2006 and my gut feeling was that somehow it was ISA 2006 that was causing the problem. I don’t have much experience with ISA 2006 and it is always easy to blame problems on the thing you know least about.
Fortunately I was investigating another SharePoint issue when I noticed that we didn’t have the output cache enabled in SharePoint. Turning on the output cache (Site Collection Administration, Output Cache Settings) and setting the Authenticated Cache Profile to Intranet (Collaboration Site) and now Extranet is performing as expected.
Looks like I will be spending a bit more time going through the SharePoint Cache documentation on Technet and its an important reminder that it easy to blame the thing you least know about when investigating an issue