Rethinking main memory OLTP recovery

Fine-grained, record-oriented write-ahead logging, as exemplified by systems like ARIES, has been the gold standard for relational database recovery. In this paper, we show that in modern high-throughput transaction processing systems, this is no longer the optimal way to recover a database system. In particular, as transaction throughputs get higher, ARIES-style logging starts to represent a non-trivial fraction of the overall transaction execution time. We propose a lighter weight, coarse-grained command logging technique which only records the transactions that were executed on the database. It then does recovery by starting from a transactionally consistent checkpoint and replaying the commands in the log as if they were new transactions. By avoiding the overhead of fine-grained logging of before and after images (both CPU complexity as well as substantial associated 110), command logging can yield significantly higher throughput at run-time. Recovery times for command logging are higher compared to an ARIEs-style physiological logging approach, but with the advent of high-availability techniques that can mask the outage of a recovering node, recovery speeds have become secondary in importance to run-time performance for most applications. We evaluated our approach on an implementation of TPCC in a main memory database system (VoltDB), and found that command logging can offer 1.5 x higher throughput than a main-memory optimized implementation of ARIEs-style physiological logging.