SES-Dedup: a Case for Low-Cost ECC-based SSD Deduplication
SES-Dedup: a Case for Low-Cost ECC-based SSD Deduplication
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DOI：
10.1109/msst.2019.00009
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发表时间：
2019-05
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影响因子：
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通讯作者：
Zhichao Yan;Hong Jiang;Song Jiang;Yujuan Tan;Hao Luo
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作者：
Zhichao Yan;Hong Jiang;Song Jiang;Yujuan Tan;Hao Luo
将重复数据删除功能集成到固态硬盘（SSD）中有助于避免将重复内容写入NAND闪存芯片，这不仅可以有效减少编程/重复（P/E）操作的数量以延长设备的使用寿命，还可以按比例扩大SSD的有效容量，以提高其幕后维护任务的性能，例如磨损均衡（WL）和垃圾收集（GC）。然而，去重的这些益处是以嵌入式SSD控制器计算加密散列所引起的不平凡的计算成本来实现的。为了解决这个开销问题，一些研究人员建议用已经嵌入在SSD芯片中的纠错码（ECC）替换加密哈希，以检测重复的内容。然而，所有现有的尝试都忽略了在现代SSD中广泛使用的数据随机化（加扰器）模块的影响，从而使得将基于ECC的去重直接集成到商业SSD中是不切实际的。在这项工作中，我们重新审视SSD的内部结构，并提出了第一个可重复数据删除的SSD，可以绕过数据加扰器模块，使低成本的ECC为基础的数据重复数据删除。具体来说，我们提出了两个设计解决方案，一个在主机端，另一个在设备端，以实现基于ECC的重复数据删除。基于我们的方法，我们可以有效地利用SSD的内置ECC模块来计算存储数据的哈希值，以进行数据重复数据删除。我们通过在SSD模拟器中重放数据跟踪来评估我们的SES-Dedup方法，发现它可以删除高达30.8%的冗余数据，与基准SSD相比，写入性能提高高达17.0%。
Integrating the data deduplication function into Solid State Drives (SSDs) helps avoid writing duplicate contents to NAND flash chips, which will not only effectively reduce the number of Program/Erase (P/E) operations to extend the device's lifespan but also proportionally enlarge the effective capacity of SSD to improve the performance of its behind-the-scenes maintenance tasks such as wear-leveling (WL) and garbage-collection (GC). However, these benefits of deduplication come at a non-trivial computational cost incurred by the embedded SSD controller to compute cryptographic hashes. To address this overhead problem, some researchers have suggested replacing cryptographic hashes with error correction codes (ECCs) already embedded in the SSD chips to detect the duplicate contents. However, all existing attempts have ignored the impact of the data randomization (scrambler) module that is widely used in modern SSDs, thus making it impractical to directly integrate ECC-based deduplication into commercial SSDs. In this work, we revisit SSD's internal structure and propose the first deduplicatable SSD that can bypass the data scrambler module to enable the low-cost ECC-based data deduplication. Specifically, we propose two design solutions, one on the host side and the other on the device side, to enable ECC-based deduplication. Based on our approach, we can effectively exploit SSD's built-in ECC module to calculate the hash values of stored data for data deduplication. We have evaluated our SES-Dedup approach by replaying data traces in an SSD simulator and found that it can remove up to 30.8% redundant data with up to 17.0% write performance improvement over the baseline SSD.