Active/active replication for highly available HPC system services

Today's high performance computing systems have several reliability deficiencies resulting in availability and serviceability issues. Head and service nodes represent a single point of failure and control for an entire system as they render it inaccessible and unmanageable in case of a failure until repair, causing a significant downtime. This paper introduces two distinct replication methods (internal and external) for providing symmetric active/active high availability for multiple head and service nodes running in virtual synchrony. It presents a comparison of both methods in terms of expected correctness, ease-of-use and performance based on early results from ongoing work in providing symmetric active/active high availability for two HPC system services (TORQUE and PVFS metadata server). It continues with a short description of a distributed mutual exclusion algorithm and a brief statement regarding the handling of Byzantine failures. This paper concludes with an overview of past and ongoing work, and a short summary of the presented research.