Persistent memory (PM) is fundamentally changing the way database index structures are built by enabling persistence, high performance, and (near) instant recovery all on the memory bus. Prior work has proposed many techniques to tailor index structure designs for PM, but they were mostly based on volatile DRAM with simulation due to the lack of real PM hardware. Until today is it unclear how these techniques will actually perform on real PM hardware. With the recent released Intel Optane DC Persistent Memory, for the first time, this paper provides a comprehensive evaluation of recent persistent index structures. We focus on B + -Tree-based range indexes and carefully choose four representative index structures for evaluation: wBTree, NV-Tree, BzTree and FPTree. These four tree structures cover a wide, representative range of techniques that are essential building blocks of PM-based index structures. For fair comparison, we used an unified programming model for all trees and developed PiBench , a benchmarking framework which targets PM-based indexes. Through empirical evaluation using representative workloads, we identify key, effective techniques, insights and caveats to guide the making of future PM-based index structures.

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Finding the best way to leverage non-volatile memory (NVM) on modern database systems is still an open problem. The answer is far from trivial since the clear boundary between memory and storage present in most systems seems to be incompatible with the intrinsic memory-storage duality of NVM. Rather than treating NVM either solely as memory or solely as storage, in this work we propose how NVM can be simultaneously used as both in the context of modern database systems. We design a persistent buffer pool on NVM, enabling pages to be directly read/written by the CPU (like memory) while recovering corrupted pages after a failure (like storage). The main benefits of our approach are an easy integration in the existing database architectures, reduced costs (by replacing DRAM with NVM), and faster peak-performance recovery.