To evaluate the reliability of a software system, measuring 'Mean-Time-between-Failure' (MTBF) and conducting an Architecture Tradeoff Analysis Method (ATAM) evaluation are appropriate methods. MTBF is a standard quantitative measure of reliability. An ATAM evaluation helps assess architectural decisions and their impact on system quality attributes, including reliability. Neither counting lines of code nor cyclomatic complexity directly assesses reliability. Performance tests measure performance, not reliability directly.