Snapshotting Mechanisms for Persistent Memory-Mapped Files
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Date
2023-09-21
Authors
Moridi, Mohammad
Journal Title
Journal ISSN
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Publisher
University of Waterloo
Abstract
In this research, we explore ways to enhance the reliability of persistent memory systems. Using Montage (ICPP'21) as our reference model, we identify areas of potential improvement, especially concerning the risk of data loss in certain failure scenarios. Our investigation led us to focus on the concept of snapshotting and its role in system resilience. We delve into various consistency models for snapshotting mechanisms and introduce a new definition for snapshotting consistency known as Buffered-Durable Consistency. Montage offers impressive resilience against system-wide crash failures. However, we perceive opportunities for further fortification, specifically when persistent memory failures occur, which can lead to substantial data loss. Addressing this challenge, we propose two new snapshotting mechanisms - stop-the-world and online snapshotting - for memory-mapped files. These mechanisms selectively replicate only those data portions that have been modified since the last snapshot, thus significantly reducing the volume of data copying during snapshot operations. In order to ensure data consistency and optimize snapshotting, we introduce modifications to both Montage and its allocator. This includes a parallel chunk-copying strategy for the stop-the-world snapshotting implementation. Additionally, our online snapshotting mechanism allows updates to chunks not being replicated by the snapshotter, which increases system responsiveness. We have also developed an algorithm that, when snapshotting is not in progress, disables the reader locks, reducing the overhead associated with such locks and further enhancing performance. To demonstrate the effectiveness of our approach, we present an experimental analysis showing throughput and latency for various scenarios. Overall, our work not only heightens the fault tolerance capabilities of Montage, but also offers critical insights and potential directions for future research and optimization in the field of persistent memory, especially for memory-mapped file replication.
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Keywords
persistent memory, data loss prevention, snapshotting mechanisms, stop-the-world snapshotting, online snapshotting, memory-mapped files, reader lock optimization, fault tolerance, data consistency models, buffered durable linearizability, buffered durable consistency