I’ve been trying to get an SSRS scale-out cluster working the past few months.  I’d given up today and resorted to calling MSFT support.  I’d read all the manuals and supplemental articles like a proper admin should.  I’d posted questions on the MSFT forums to no avail.  Time to bite the bullet and sit on the phone with an expert.

I was getting 401 errors with not much help from the error logs.  A 401 is a security error.  The problem was intermittent, sometimes happening, sometimes not.  The problem always went away when a node was removed from the load balancer rotation.  Major hint there.  When you connect to the load balancer, you are routed to the same SSRS node – until you time out at 10 minutes – this is called “Sticky Sessions”.  The SSRS servers also got this treatment from the load balancer – and that was the problem.

The tech and I went through hours of checking configurations until he asked me to add an entry to the hosts file for the F5 name which reporting services was using.  This would make node 1 always request data from SSRS on node 1 and node 2 always request data from node 2.  Fixed the issue.  I imagine we can configure this on the load balancer as well, which I will probably have done.