NF-Log: Revisiting Log Writes in relational database for efficient persistent memory utilization

Non-volatile memory (NVM) is a promising storage technology that combines not only high performance and byte-addressability (like DRAM) but also durability (like SSD). However, as existing relational database management systems (RDBMS) are originally designed based on the assumption that all the data and log are stored on high latency block based devices, they are not able to take full advantage of this new technology yet. Consequently, write operations will under-utilize the device(NVM) and eventually downgrade the performance. In this work, we analyzed the redo-log mechanism in InnoDB and after discovering its severe impact on the overall performance, we decided to perform optimizations that will match with NVM features. We started by re-designing the log write path within InnoDB. After that, we worked on improving the log data access locality and finally, we optimized the write ahead mechanism. NFlog (Non Flushing Log) utilizes the NVM byte addressability and its persistence feature to reduce the write size by 30% and boost up the performance to up to 38% for sysbench write_intensive workloads and up to 16% for TPC-C.