This paper considers stochastic modeling for performance evaluation of real-time fault-tolerant software systems. N-version(NV)software system and recovery block(RB)software system are widely-known as the methodologies of fault-tolerant software systems. Many researchers have been discussing their performance and reliability. In this paper, by introducing the propery of real-time into the NV and RB software systems, we derive several measures for performance evaluation, and study the relation between the real-time property and their performance by using several numerical examples.