Track-based Translation Layers for Interlaced Magnetic Recording
Track-based Translation Layers for Interlaced Magnetic Recording
复制标题
用于隔行磁记录的基于磁道的转换层
DOI：
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发表时间：
2019
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通讯作者：
Timothy R. Feldman
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作者：
Mohammad Hossein Hajkazemi;A. Kulkarni;Peter Desnoyers;Timothy R. Feldman
隔行磁记录 (IMR) 是一种最先进的硬盘记录技术，它利用热辅助磁记录 (HAMR) 和磁道重叠来提供比传统磁记录和叠瓦磁记录（CMR 和 SMR）更高的容量。它带有一组与 SMR 不同的写入约束：“底部”（例如偶数编号）磁道无法在相邻“顶部”（例如奇数编号）磁道上的数据丢失的情况下写入。先前描述的用于在 IMR 上写入任意（即底部）扇区的算法在某些情况下特征很差，并且要么速度慢，要么需要比受限磁盘控制器环境中可用的内存更多的内存。我们对 IMR 底部磁道写入的简单读取-修改-写入 (RMW) 方法进行了首次准确的性能分析，注意到早期性能描述中的一些不准确之处，并评估了它在实际跟踪中的延迟、吞吐量和 I/O 放大。此外，我们为 IMR 提出了三种新颖的内存高效、基于磁道的转换层——磁道翻转、选择性磁道缓存和动态磁道映射，它们通过以不同方式将热数据移动到顶部磁道并将冷数据移动到底部磁道来减少底部磁道写入。我们再次使用基于真实世界轨迹的模拟来提供详细的性能分析。我们发现 RMW 性能在大多数轨迹上都很差，在其他轨迹上更差。所提出的方法性能要好得多，尤其是动态磁道映射，对于许多磁道而言，写入放大和延迟与 CMR 相当。
Interlaced magnetic recording (IMR) is a state-of-the-art recording technology for hard drives that makes use of heat-assisted magnetic recording (HAMR) and track overlap to offer higher capacity than conventional and shingled magnetic recording (CMR and SMR). It carries a set of write constraints that differ from those in SMR: “bottom” (e.g. even-numbered) tracks cannot be written without data loss on the adjoining “top” (e.g. odd-numbered) ones. Previously described algorithms for writing arbitrary (i.e. bottom) sectors on IMR are in some cases poorly characterized, and are either slow or require more memory than is available within the constrained disk controller environment. We provide the first accurate performance analysis of the simple read-modify-write (RMW) approach to IMR bottom track writes, noting several inaccuracies in earlier descriptions of its performance, and evaluate it for latency, throughput and I/O amplification on real-world traces. In addition we propose three novel memory-efficient, track-based translation layers for IMR— track flipping , selective track caching and dynamic track mapping , which reduce bottom track writes by moving hot data to top tracks and cold data to bottom ones in different ways. We again provide a detailed performance analysis using simulations based on real-world traces. We find that RMW performance is poor on most traces and worse on others. The proposed approaches perform much better, especially dynamic track mapping, with low write amplification and latency comparable to CMR for many traces.