Recent advances in flash memory technology have reduced the cost-per-bit of flash storage devices such as solid-state drives (SSDs), thereby enabling the development of large-capacity SSDs for enterprise-scale storage. However, two major concerns arise in designing SSDs. First, the size of the address mapping table is increasing in proportion to the capacity of the SSD. The SSD-internal firmware, called flash translation layer (FTL), must maintain the address mapping table in the internal DRAM. Although the previously proposed demand map loading technique uses a small size of cached map table, the technique aggravates poor random performance. Second, there are many redundant writes in storage workloads, which have an adverse effect on the performance and lifetime of the SSD. For example, many transaction-supporting applications use the write-ahead-log (WAL) scheme, which writes the same data twice. To resolve these problems, we propose a novel transaction-supporting SSD, called WAL-SSD, which logs transaction data at the internally-managed WAL area and relocates the data atomically via the FTL-level remap operation at the transaction checkpointing. It can also be used to transform random write requests to sequential requests. We implemented a prototype of WAL-SSD with a real SSD device. Experiments demonstrate the performance improvement by WAL-SSD with three use cases: remap-journaling, atomic multi-block update, and random write logging.

中文翻译：

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WAL-SSD：基于地址重映射的预写日志固态磁盘

闪存技术的最新进展降低了固态硬盘 (SSD) 等闪存存储设备的每比特成本，从而为企业级存储开发了大容量 SSD。然而，在设计 SSD 时出现了两个主要问题。首先，地址映射表的大小与SSD的容量成比例增加。SSD 内部固件，称为闪存转换层 (FTL)，必须在内部 DRAM 中维护地址映射表。虽然之前提出的需求地图加载技术使用了小尺寸的缓存地图表，但该技术加剧了较差的随机性能。其次，存储工作负载存在大量冗余写入，对SSD的性能和寿命产生不利影响。例如，许多支持事务的应用程序使用预写日志 (WAL) 方案，该方案将相同的数据写入两次。为了解决这些问题，我们提出了一种新的支持事务的 SSD，称为 WAL-SSD，它在内部管理的 WAL 区域记录事务数据，并在事务检查点通过 FTL 级重映射操作原子地重新定位数据。它还可以用于将随机写入请求转换为顺序请求。我们使用真正的 SSD 设备实现了 WAL-SSD 的原型。实验通过三个用例证明了 WAL-SSD 的性能改进：重映射日志、原子多块更新和随机写入日志。它在内部管理的 WAL 区域记录事务数据，并在事务检查点通过 FTL 级重映射操作原子地重新定位数据。它还可以用于将随机写入请求转换为顺序请求。我们使用真正的 SSD 设备实现了 WAL-SSD 的原型。实验通过三个用例证明了 WAL-SSD 的性能改进：重映射日志、原子多块更新和随机写入日志。它在内部管理的 WAL 区域记录事务数据，并在事务检查点通过 FTL 级重映射操作原子地重新定位数据。它还可以用于将随机写入请求转换为顺序请求。我们使用真正的 SSD 设备实现了 WAL-SSD 的原型。实验通过三个用例证明了 WAL-SSD 的性能改进：重映射日志、原子多块更新和随机写入日志。