• KIPS Transactions on Computer and Communication Systems
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• v.8 no.7
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• pp.159-166
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• 2019

Unlike modern Solid-State Drives with DRAM, DRAM-less SSDs do not have DRAM because they are cheap and consume less power. Obviously, they have performance degradation problem due to lack of DRAM in the controller and this problem can be alleviated by utilizing host memory buffer(HMB) feature of NVMe, which allows SSDs to utilize the DRAM of host. In this paper, we show that commercial DRAM-less SSDs surely exhibit lower I/O performance than other SSDs with DRAM, but they can be improved by utilizing the HMB feature. Through various experiments and analysis, we also show that DRAM-less SSDs mainly exploit the DRAM of host as mapping table cache rather than read cache or write buffer to improve I/O performance.

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.509-514
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• 2009

In this paper, we designed and analyzed 256GB DRAM-based SSD storage using DDR1 memory and PCI-e interface. SSD is a storage system that uses DRAM or NAND Flash as primary storage media. Since the SSD read and write data directly to memory chips, which results in storage speeds far greater than conventional magnetic storage devices, HDD. Architecture of the proposed SSD system has performance of high speed data processing duo to use multiple RAM disks as primary storage and PCI-e interface bus as communication path of RAM disks. We constructed experimental system with UNIX, Windows/Linux server, SAN Switch, and Ethernet Switch and measured IOPS and bandwidth of proposed SSD using IOmeter. In experimental results, it has been shown that IOPS, 470,000 and bandwidth,800MB/sec of the DDR-1 SSD is better than those of the HDD and Flash-based SSD.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.11-15
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• 2015

SSD(Solide State Disk) Memory is gradually replacing HDD(Hard Disk Drive) for high speed data input and output processing on Internet server system. In this paper, we proposed efficient data distribution storage algorithm in DRAM based SSD. And we did performance test for proposed algorithm and existing algorithm in the same server environment condition. The result of comparison of performance test is as fellows. Data backup processing time of proposed algorithm was reduced by half than that of existing algorithm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.7
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• pp.48-56
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• 2011

Recently, new storage device SSD(Solid State Disk) based on NAND flash memory is gradually replacing HDD(Hard Disk Drive) in mobile device and thus a variety of research efforts are going on to find the cost-effective ways of performance improvement. By increasing the NAND flash channels in order to enhance the bandwidth through parallel processing, DRAM buffer which acts as a buffer cache between host(PC) and NAND flash has become the bottleneck point. To resolve this problem, this paper proposes an efficient low-cost scheme to increase SSD performance by improving DRAM buffer bandwidth through scheduling techniques which utilize DRAM multi-banks. When both host and NAND flash multi-channels request access to DRAM buffer concurrently, the proposed technique checks their destination and then schedules appropriately considering properties of DRAMs. It can reduce overheads of bank active time and row latency significantly and thus optimizes DRAM buffer bandwidth utilization. The result reveals that the proposed technique improves the SSD performance by 47.4% in read and 47.7% in write operation respectively compared to conventional methods with negligible changes and increases in the hardware.

• Journal of KIISE
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• v.42 no.1
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• pp.107-113
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• 2015

In a database system, updates on pages that are made by a transaction should be stored in a secondary storage before the commit is complete. Generic secondary storages have volatile DRAM caches to hide long latency for non-volatile media. However, as logs that are only written to the volatile DRAM cache don't ensure durability, logging latency cannot be hidden. Recently, a flash SSD with capacitor-backed DRAM cache was developed to overcome the shortcoming. Storage devices, like those with a non-volatile cache, will increase transaction throughput because transactions can commit as soon as the logs reach the cache. In this paper, we analyzed performance in terms of transaction throughput when the SSD with capacitor-backed DRAM cache was used as log storage. The transaction throughput can be improved over three times, by committing right after storing the logs to the DRAM cache, rather than to a secondary storage device. Also, we showed that it could acquire over 73% of the ideal logging performance with proper tuning.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.7
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• pp.57-64
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• 2011

To adjust the difference of bandwidth between host interface and NAND flash memory, DRAM is adopted as the buffer management in SSD (Solid-state Disk). In this paper, we propose cost-effective techniques to enhance SSD performance instead of using expensive high bandwidth DRAM. The SSD data can be classified into three groups such as user data, meta data for handling user data, and FEC(Forward Error Correction) parity/ CRC(Cyclic Redundancy Check) for error control. In order to improve the performance by considering the features of each data, we devise a flexible burst control method through monitoring system and a page based FEC parity/CRC application. Experimental results show that proposed methods enhance the SSD performance up to 25.9% with a negligible 0.07% increase in chip size.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.07a
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• pp.3-4
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• 2017

DRAM, HDD의 성장세가 둔화되면서 NVM이 그 대안으로 떠오르고 있다. Xpoint, Z-SSD등 여러 고성능 NVM이 발표되고 있으며 DRAM의 성능을 목표로 하고 있다. 본 논문에서는 DRAM 수준의 고성능 NVM이 상용화 될 때 어느 정도의 성능과 가격지표를 보일 것이며 이에 대한 가격과 저장공간의 트레이드오프는 어느 정도일지 알아보기 위해 실험을 진행하였다. RAM disk로 NVM환경을 시뮬레이션 하였고 SSD, HDD 간 I/O 성능을 측정하였다. NVM과 SSD는 70배에서 200배, NVM과 디스크는 98배에서 3000배 이상 차이가 있음을 확인했다. 이 결과를 바탕으로 RAM disk와 SSD 가격지표를 조사하여 IOPS/$를 도출해 보았고 NVM이 7배의 IOPS/$를 가지지만 SSD가 18배의 GB/$를 가지는 것을 확인할 수 있었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.288-289
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• 2012

최근 데이터 저장을 위한 고속 입출력에서 병목현상을 해결하기 위해 다양한 SSD(Solid State Drive) 관련 연구가 많이 수행되고 있다. 대표적인 것으로 비휘발성 메모리인 플래시와 차세대 반도체 메모리인 SCM(Storage Class Memory) SSD가 있고, 휘발성 메모리인 DRAM기반의 SSD가 있다. 플래시 또는 SCM 메모리기반 저장장치는 하드 디스크기반 저장장치에 비해 읽기 속도가 빠르며, 내구성이 강하다는 장점으로 새로운 저장장치 시스템의 저장매체로 부각되고 있으나, 단위 저장 공간 당 높은 가격으로 인해 저장장치 시스템에 적용하기 에는 많은 문제점이 있다. 최근에는 이러한 문제를 해결하기 위해 고용량의 하드디스크와 SSD를 RAID 또는 단일 저장장치 매체로 구성하는 하이브리드 저장장치에 관한 연구와 제품이 출시되고 있다. 본 논문에서는 이러한 하이브리드 저장 매체 어레이를 저장장치 시스템으로 구성하기 위한 볼륨구성과 해당 서버에 볼륨 제공 서비스를 수행하기 위한 하이브리드 저장장치 시스템 설계 방법에 대해 설명한다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.4
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• pp.117-123
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• 2013

In the recent cloud storage environment, the amount of SSD (Solid-State Drive) replacing with the traditional hard disk drive is increasing. Management of SSD for its space efficiency has become important since SSD provides fast IO performance due to no mechanical movement whereas it has wearable characteristics and does not provide in place update. In order to manage space efficiency of SSD, data de-duplication technique is frequently used. However, this technique occurs much overhead because it consists of data chunking, hasing and hash matching operations. In this paper, we propose new data de-duplication method using PRAM cache. The proposed method uses hierarchical hash tables and LRU(Least Recently Used) for data replacement in PRAM. First hash table in DRAM is used to store hash values of data cached in the PRAM and second hash table in PRAM is used to store hash values of data in SSD storage. The method also enhance data reliability against power failure by maintaining backup of first hash table into PRAM. Experimental results show that average writing frequency and operation time of the proposed method are 44.2% and 38.8% less than those of existing data de-depulication method, respectively, when three workloads are used.

• Journal of Internet of Things and Convergence
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• v.9 no.1
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• pp.71-76
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• 2023

Recently, in order to store and manage big data, research and development of a high-performance storage system capable of stably accessing large data have been actively conducted. In particular, storage systems in data centers and enterprise environments use large amounts of SSD (solid state disk) to manage large amounts of data. In general, SSD uses FTL(flash transfer layer) to hide the characteristics of NAND flash memory, which is a medium, and to efficiently manage data. However, FTL's algorithm has a limitation in using DRAM more to manage the location information of NAND where data is stored as the capacity of SSD increases. Therefore, this paper introduces FTL policies that apply virtual memory to reduce DRAM resources used in FTL. The virtual memory-based FTL policy proposed in this paper manages the map data by using LRU (least recently used) policy to load the mapping information of the recently used data into the DRAM space and store the previously used information in NAND. Finally, through experiments, performance and resource usage consumed during data write processing of virtual memory-based FTL and general FTL are measured and analyzed.