  Root cause analysis (RCA) is crucial for enhancing the reliability and
performance of complex systems. However, progress in this field has been
hindered by the lack of large-scale, open-source datasets tailored for RCA. To
bridge this gap, we introduce LEMMA-RCA, a large dataset designed for diverse
RCA tasks across multiple domains and modalities. LEMMA-RCA features various
real-world fault scenarios from IT and OT operation systems, encompassing
microservices, water distribution, and water treatment systems, with hundreds
of system entities involved. We evaluate the quality of LEMMA-RCA by testing
the performance of eight baseline methods on this dataset under various
settings, including offline and online modes as well as single and multiple
modalities. Our experimental results demonstrate the high quality of LEMMA-RCA.
The dataset is publicly available at https://lemma-rca.github.io/.
