High-performance storage devices, such as Non-Volatile Memory express Solid-State Drives (NVMe SSDs), have been widely adopted in data centers. Especially, multiple storage devices provide higher I/O performance compared with a single device. However, the performance can be reduced in the case of workloads with mixed read and write requests (e.g., key-value stores) even though multiple storage devices are adopted. This is because read requests can be blocked until the processing for write requests is finished. In this article, we propose an I/O isolation scheme to improve the performance of the key-value store for multiple SSDs. In our scheme, we classify files of the key-value store and deploy files to the separated storage devices according to the characteristics of each file. Thus, read/write operations are performed in different storage devices. In addition, we propose two different device mapping methods, namely fixed and adaptive device mapping to deploy files to the proper device. We implement our scheme in RocksDB with multiple storage devices (six NVMe SSDs) and extend our scheme on an open-channel SSD, which reveals internal hardware architecture to verify the effectiveness of read/write isolation within a single storage device. The experimental results demonstrate that our scheme improves performance by up to 29% and 26% in the open-channel SSD and multiple storage devices, respectively, compared with the existing scheme.

高性能存储设备，例如非易失性内存表达固态驱动器（NVMe SSD），已被数据中心广泛采用。特别是，与单个设备相比，多个存储设备可提供更高的I / O性能。但是，即使采用多个存储设备，在具有混合读写请求（例如键值存储）的工作负载的情况下，性能也会降低。这是因为在完成写请求的处理之前，可以阻止读请求。在本文中，我们提出了一种I / O隔离方案，以提高多个SSD的键值存储的性能。在我们的方案中，我们对键值存储的文件进行分类，然后根据每个文件的特征将文件部署到单独的存储设备中。从而，读/写操作在不同的存储设备中执行。另外，我们提出了两种不同的设备映射方法，即将文件部署到适当设备的固定设备映射和自适应设备映射。我们在具有多个存储设备（六个NVMe SSD）的RocksDB中实现我们的方案，并在开放通道SSD上扩展我们的方案，这揭示了内部硬件体系结构，以验证单个存储设备中的读/写隔离的有效性。实验结果表明，与现有方案相比，我们的方案在开放通道SSD和多个存储设备中的性能分别提高了29％和26％。我们在具有多个存储设备（六个NVMe SSD）的RocksDB中实现我们的方案，并在开放通道SSD上扩展我们的方案，这揭示了内部硬件体系结构，以验证单个存储设备中的读/写隔离的有效性。实验结果表明，与现有方案相比，我们的方案在开放通道SSD和多个存储设备中的性能分别提高了29％和26％。我们在具有多个存储设备（六个NVMe SSD）的RocksDB中实现我们的方案，并在开放通道SSD上扩展我们的方案，这揭示了内部硬件体系结构，以验证单个存储设备中的读/写隔离的有效性。实验结果表明，与现有方案相比，我们的方案在开放通道SSD和多个存储设备中的性能分别提高了29％和26％。