Symptoms

KB001221 "How to switch off the K2 server discovery feature" which is marked as applicable to all versions of K2 from 4.6 to 4.6.10 suggest editing of DiscoveryService.config file. But this article does not say that starting from K2 blackpearl 4.6.9 (clean installation) and onwards there is no discoveryservice.config file.
 

Diagnoses

In K2 blackpearl version 4.6.9, a number of configuration files have been consolidated into a single configuration file to simplify the management of configuration settings. Please refer to KB001637 "Configuration file consolidation in K2 blackpearl 4.6.9" for details on this.
 

Resolution

Starting from version 4.6.9 (clean installation) you have to set most of configuration settings in K2HostServer.exe.Config file.