In this paper, we have analyzed a two-unit warm standby system with various types of failure and instruction. There are three types of failures that have been considered: operating unit or the warm standby unit failure, failure due to common error and the failure due to human error. There is repair faculty available for the repair of the failed unit. In case the repairman is unable to repair the failed unit, an expert repairman is called for the repair of the failed unit. Using semi-Markov process and regenerative point technique, various reliability measures have been derived. Also, the comparison analysis has been drawn graphically.