The Lsass.exe process is seen as a big black box by many, using more resources than would be expected. In reality, it is a process like any other which simply takes care of many core aspects of the operating system on any computer, and the additional roles that a domain controller has on a DC. Some of the things which are done in that "black box" are peer domain controller location, authentication, authorization and Active Directory replication.
What about Server Performance Advisor (SPA), you ask? I’ve mentioned using the SPA tool in my blog post “A Day at the SPA” but the SPA AD Data Collector is not the tool for every performance related problem which exists.