• 대한임베디드공학회논문지
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• 제12권3호
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• pp.169-176
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• 2017

To replace conventional DRAM, many researches have been done on nonvolatile memories. The DRAM&PCM hybrid memory is one of the effective structure because it can utilize an advantage of DRAM and PCM. However, in order to use this characteristics, pages can be replaced frequently between DRAM and PCM. Therefore, PCM still has major problem that has write-limits. Therefore, it needs an effective page management method for exploiting each memory characteristics dynamically and adaptively. So we aim reducing an average access time and write count of PCM by utilizing two locality for an effective page replacement. We proposed a page selection algorithm which is recently requested to write in DRAM and an algorithm witch uses two locality in PCM. According to our simulation, the proposed algorithm for the DRAM&PCM hybrid can reduce the PCM write count by around 22% and the average access time by 31% given the same PCM size, compared with CLOCK-DWF algorithm.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.932-935
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• 2002

In this paper, we introduce new FTL(Flash Translation Layer) driver algorithm that tolerate the power off errors. FTL driver is the software that provide the block device interface to the upper layer software such as file systems or application programs that using the flash memory as a block device interfaced storage. Usually, the flash memory is used as the storage devices of the mobile system due to its low power consumption and small form factor. In mobile system, the state of the power supplement is not stable, because it using the small sized battery that has limited capacity. So, a sudden power off failure can be occurred when we read or write the data on the flash memory. During the write operation, power off failure may introduce the incomplete write operation. Incomplete write operation denotes the inconsistency of the data in flash memory. To provide the stable storage facility with flash memory in mobile system, FTL should provide the fault tolerance against the power off failure. SSR (Simple Sector Remapper) is a fault tolerant FTL driver that provides block device interface and also provides tolerance against power off errors.

• 한국컴퓨터정보학회논문지
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• 제23권3호
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• pp.1-8
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• 2018

In this paper, we propose a new page replacement policy using recency and frequency on hybrid main memory. The proposal has two features. First, when a page fault occurs in the main memory, the proposal allocates it to DRAM, regardless of operation types such as read or write. The page allocated by the page fault is likely to be high probability of re-reference in the near future. Our allocation can reduce the frequency of write operations in PCM. Second, if the write operations are frequently performed on pages of PCM, the pages are migrated from PCM to DRAM. Otherwise, the pages are maintained in PCM, to reduce the number of unnecessary page migrations from PCM. In our experiments, the proposal reduced the number of page migrations from PCM about 32.12% on average and reduced the number of write operations in PCM about 44.64% on average, compared to CLOCK-DWF. Moreover, the proposal reduced the energy consumption about 15.61%, and 3.04%, compared to other page replacement policies.

• 한국인터넷방송통신학회논문지
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• 제14권1호
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• pp.15-21
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• 2014

반도체 공정 기술의 발달로 인하여 프로세서 내에 적재할 수 있는 캐쉬 메모리의 용량은 증가하였지만 높은 트랜지스터 집적율은 프로세서를 소프트 에러에 대해 더 취약하게 만들었으며, 이는 설계 고려사항 중 신뢰성의 비중이 점점 더 높아짐을 의미한다. 이러한 취약성을 극복하기 위하여 캐쉬 메모리의 데이터에 대한 다양한 신뢰성 기법이 제안되었으나, 태그 비트에 대한 연구는 제한적이다. 본 연구는 캐쉬 메모리 중 태그 비트에 대해 Temporal Locality 특성을 만족하지 않는 write-back 동작에 대한 보호율을 분석하고, 이를 극복할 수 있는 방안을 제안한다. 실험을 통해 제안된 기법으로 기존의 write-back에 대한 보호율을 59.0%에서 76.8%까지 성능 저하 없이 증가시킬 수 있다.

• 대한임베디드공학회논문지
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• 제11권2호
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• pp.67-78
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• 2016

The emerging Spin-Transfer Torque RAM (STT-RAM) is a promising component that can be used to improve the efficiency as a result of its high storage density and low leakage power. However, the state-of-the-art STT-RAM is not ready to replace SRAM technology due to the negative effect of its write operations. The write operations require longer latency and more power than the same operations in SRAM. Therefore, a hybrid cache with SRAM and STT-RAM technologies is proposed to obtain the benefits of STT-RAM while minimizing its negative effects by using SRAM. To efficiently use of the hybrid cache, it is important to place write intensive data onto the cache. Such data should be placed on SRAM to minimize the negative effect. Thus, we propose a technique that optimizes placement of data in main memory. It drives the proper combination of advantages and disadvantages for SRAM and STT-RAM in the hybrid cache. As a result of the proposed technique, write intensive data are loaded to SRAM and read intensive data are loaded to STT-RAM. In addition, our technique also optimizes temporal locality to minimize conflict misses. Therefore, it improves performance and energy consumption of the hybrid cache architecture in a certain range.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2005년도 추계 종합학술대회 논문집
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• pp.234-238
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• 2005

WSDL은 XML로 웹 서비스를 어떻게 기술하여야 하는 것을 정의하는 사양이다. WSDL을 이용하여 클라이언트는 웹 서비스를 발견하고 웹 서비스가 제공하는 공개함수를 호출할 수 있다. 본 논문에서는 전표데이터 처리를 제공하는 간단한 서비스에 대한 WSDL 정의 응용을 보여 준다. 이 서비스는 HTTP상에 SOAP 프로토콜을 사용하여 구축된 WriteSlipXMLFromSql, WriteSlipXMLFromSqlProc, Insert SlipDataToDb 라고 하는 3개의 웹 메소드를 지원한다. 본 논문의 결과는 전자상거래 시스템 구축의 주요플랫폼인 웹 서비스의 효율적인 개발에 기여할 것으로 전망된다.

• Journal of Computing Science and Engineering
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• 제11권3호
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• pp.92-99
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• 2017

Memcached, commonly used to speed up the data access in big-data and Internet-web applications, is a system software of the distributed-cache mechanism. But it is subject to the severe challenge of the loss of recently uncommitted updates in the case where the Memcached servers crash due to some reason. Although the replica scheme and the disk-log-based replay mechanism have been proposed to overcome this problem, they generate either the overhead of the replica synchronization or the persistent-storage overhead that is caused by flushing related logs. This paper proposes a scheme of backing up the write requests (i.e., set and add) on the Memcached client side, to reduce the overhead resulting from the making of disk-log records or performing the replica consistency. If the Memcached server fails, a timestamp-based recovery mechanism is then introduced to replay the write requests (buffered by relevant clients), for regaining the lost-data updates on the rebooted Memcached server, thereby meeting the data-consistency requirement. More importantly, compared with the mechanism of logging the write requests to the persistent storage of the master server and the server-replication scheme, the newly proposed approach of backing up the logs on the client side can greatly decrease the time overhead by up to 116.8% when processing the write workloads.

• Journal of Magnetics
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• 제6권4호
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• pp.109-118
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• 2001

A computer simulation, utilizing the Landau-Lifshitz-Gilbert equation, of ultra-high- density recording on continuous longitudinal media is carried out. The two important features of this work are the use of a planar-type head, which enables a high write field of 14183 Oe ts be generated at the center of the recording medium, and the media with very high coercivities up to 13010 Oe. From a systematic investigation, it is found that the optimum write field is higher than the medium coercivity by only 3400 Oe over a wide coercivity range. This new finding allows one to write an a medium with a very high coercivity by using a planar-type head. It is demonstrated that a reasonably good bit pattern with a bit density of 605 kfci is generated on the medium with a coercivity of l1720 Oe, and, combined with a high track pitch density of 100 ktpi, a recording density of 60 Gb/in$^2$can be obtained in a single layer medium. With an improved write- head designs even a higher recording density of 75 Gb/in$^2$may be possible since comparison of the results for the bit pattern from the present head profile and the ideal Lindholm profile indicates an increase in the track pitch density of about 27%. Even at this density, the thermal stability parameter (KV/kT) at room temperature is high enough (60) to provide ample room for thermal stability.

• Journal of Information Processing Systems
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• 제7권1호
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• pp.53-62
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• 2011

With the steady growth of mobile technology and applications, demand for more storage in mobile devices has also increased. A lightweight block-level protocol, Internet Advanced Technology Attachment (iATA), has been developed to deliver a cost-effective storage network solution for mobile devices to obtain more storage. This paper seeks to contribute to designing and implementing Load Balancing (LB), Network Monitoring (NM) and Write Replication (WR) modules to improve the protocol's scalability and data availability. LB and NM modules are invoked to collect system resources states and current network status at each associate node (server machine). A dynamic weight factor is calculated based on the collected information and sent to a referral server. The referral server is responsible to analyze and allocate the most ideal node with the least weight to serve the client. With this approach, the client can avoid connecting to a heavily loaded node that may cause delays in subsequent in-band I/O operations. Write replication is applied to the remaining nodes through a WR module by utilizing the Unison file synchronization program. A client initially connected to node IP A for write operations will have no hindrances in executing the relevant read operations at node IP B in new connections. In the worst case scenario of a node crashing, data remain recoverable from other functioning nodes. We have conducted several benchmark tests and our results are evaluated and verified in a later section.

• 한국전자통신학회논문지
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• 제7권6호
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• pp.1493-1498
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• 2012

RFID는 유비쿼터스 환경을 구축하기 위한 핵심적인 기술이다. RFID 태그가 널리 사용됨에 따라 대량의 태그에 데이터를 신속하게 기록하는 기술이 필요하다. 태그에 대한 쓰기는 미세 전파를 이용하기 때문에 실패하는 경우가 흔히 발생한다. 본 논문에서는 대량의 RFID 태그에 데이터를 기록함에 있어 효율적으로 태그 데이터를 쓰기 위한 기법을 제시한다. 제안하는 기법은 RFID 미들웨어에 연결된 다수의 리더를 병렬적으로 배치하고 태그에 대한 동시 쓰기 작업을 수행한다. 리더별로 쓰기 작업을 분산시키고 태그들을 그룹으로 구분하여 쓰기를 수행한다. 실험을 통해 제안하는 기법이 대량의 태그 쓰기에 대한 성공률을 높일 수 있음을 보였다.