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Distributed Storage System for Reducing Write Amplification on Non-Volatile Memory
http://doi.org/10.5626/JOK.2020.47.2.129
Recently, research on non-volatile memory, such as 3DXpoint, in distributed storage systems has received considerable interest from both academia and industry. However, in order to utilize these state-of-the-art non-volatile memory devices effectively in distributed storage systems, there is a need for improvements in traditional architectures of HDD/SSD-based storage systems. This is because current distributed storage system structures use a dedicated space for journaling to make up for slow storage performance. Also, considering the performance characteristics of non-volatile memory, which are similar to that of DRAM, current distributed storage system structures are not only inefficient in terms of overall performance but also cause write amplification. In this paper, we propose an architecture that mitigates the effects of write amplification in non-volatile memory-based distributed storage systems. To evaluate the proposed architecture and scheme, we have conducted diverse experiments in a CEPH storage system environment. Through these experiments, we have confirmed that the DAXNJ structure proposed in this paper decreases write amplification by 61% during 1M object write operations and increases the overall system performance by 15%.
An Efficient SLC-buffer Management Scheme for TLC NAND Flash-based Storage
Kirock Kwon, Dong Hyun Kang, Young Ik Eom
http://doi.org/10.5626/JOK.2018.45.7.611
In recent years, almost all consumer devices have adopted NAND flash storage as their main storage, and their performance and capacity requirements are getting higher. To meet these requirements, many researchers have focused on combined SLC-TLC storage consisting of high-speed SLC and high-density TLC. In this paper, we redesign the internal structure of the combined SLC-TLC storage to efficiently manage the SLC region inside the storage and propose a scheme that improves the performance of the storage by employing the I/O characteristics of file system journaling. We implemented our scheme on the real storage platform, the OpenSSD jasmine board, and compared it with the conventional techniques. Our evaluation results show that our technique improves the storage performance by up to 65%, compared with the conventional techniques.
Consideration of fsync() of the Ext4 File System According to Kernel Version
Seongbae Son, Yoenjin Noh, Dokeun Lee, Sungsoon Park, Youjip Won
Ext4 file system is widely used in various computing environments such as those of the PC, the server, and the Linux-based embedded system. Ext4, which uses a buffer for block I/O, provides fsync() system call to applications to guarantee the consistency of a specific file. A log of the analytical studies regarding the operation of Ext4 and the improvement of its performance has been compiled, but it has not been studied in detail in terms of kernel versions. We figure out that the behavior of fsync() system call is different depending on the kernel version. Between the kernel versions of 3.4.0 and 4.7.2, 3.4.0, 3.8.0, and 4.6.2 showed behavioral differences regarding the fsync() system call. The latency of fsync() in kernel 3.4.0 is longer than that of the more-advanced 3.7.10; meanwhile, the characteristics of 3.8.0 enabled the disruption of the Ext4 journaling order, but the ordered defect was solved with 4.6.2.
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