• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.21-30
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• 2009

Fusion flash memory such as OneNAND$^{TM}$ is popular as a ubiquitous storage device for embedded systems because it has advantages of NAND and NOR flash memory that it can support large capacity, fast read/write performance and XIP(eXecute-In-Place). Besides, OneNAND$^{TM}$ provides not only advantages of hybrid structure but also multi-block erase function that improves slow erase performance by erasing the multiple blocks simultaneously. But traditional NAND Flash Translation Layer may not fully support it because the garbage collection of traditional FTL only considers a few block as victim block and erases them. In this paper, we propose an Erase Group Flash Translation Layer for improving multi-block erase function. EGFTL uses a superblock scheme for enhancing garbage collection performance and invalid block management to erase multiple blocks simultaneously. Also, it uses clustered hash table to improve the address translation performance of the superblock scheme. The experimental results show that the garbage collection performance of EGFTL is 30% higher than those of traditional FTLs, and the address translation performance of EGFTL is 5% higher than that of Superblock scheme.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.647-648
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• 2008

Traditional FTL and flash file systems based of NAND flash memory may not be adaptively applied to new fusion flash memory which combines the advantages of NAND and NOR flash memory. In this paper, we propose a FTL performance measurement tool using Multi Block Erase function of fusion flash memory. The performance measurement tool shows that multi block erase function can be effectively utilized in performance enhancement of garbage collection for fusion flash memory.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.7
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• pp.425-432
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• 2014

This paper proposes a wear-leveling algorithm that exploits the properties of SSD memories with multi-channel and multi-way architecture. When a write request arrives, the proposed algorithm classifies the stored data in DRAM buffer into hot or cold according to logical address access frequency, and performs data allocation to reduce deviation of block erase counts. It lowers the chance of increasing erase count by allocating cold data to blocks which have high erase count. Effectiveness of the proposed algorithm is verified by executing various applications on a multi-channel, multi-way SSD simulator. Experimental results show that differences in erase count among blocks is reduced by an average of 9.3%, and total erase count decreases by 4.6%, when compared to previous wear-leveling algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.108-114
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• 2008

Since flash memory cannot be overwritten, new data are updated in new area. If data are frequently updated, garbage collection which is achieved by erasing blocks, should be performed to reclaim new area. Hence, because the count of erase operations is limited due to characteristics of flash memory, every block should be evenly written and erased. However, if data with access locality are processed by cost benefit algorithm with separation of hot block ad cold block though the performance of processing is hight wear-leveling is not even. In this paper, we propose CB-MB (Cost Benefit between Multi Bank) algorithm in which hot data are allocated in one bank and cold data in another bank, and in which role of hot bank and cold bank is exchanged every period. CB-MB shows that its performance is 30% better than cost benefit algorithm with separation of cold block and hot block its wear-leveling is about a third of that in standard deviation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.574-577
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• 2007

While disk can be overwritten on updating data, because flash memory can not be overwritten on updating data, new data are updated in new area. If data are frequently updated, garbage collection, which is achieved by erasing blocks, should be performed to reclaim new area. Hence, because the number of erase operations is limited due to characteristics of flash memory, every block should be evenly written and erased. However, if data with access locality are processed by cost benefit algorithm with separation of hot block and cold block, though the performance of processing is high, wear-leveling is not even. In this paper, we propose CB-MB (Cost Benefit between Multi Bank) algorithm in which hot data are allocated in one bank and cold data in another bank, and in which role of hot bank and cold bank is exchanged every period. CB-MB showed that its performance was similar to that of others for uniform workload, however, the method provides much better performance than that of others for workload of access locality.

• Journal of Information Technology Applications and Management
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• v.11 no.2
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• pp.29-43
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• 2004

As the development of an information technique, gradually, mobile device is going to be miniaturized and operates at high speed. By such the requirements, the devices using a flash memory as a storage media are increasing. The flash memory consumes low power, is a small size, and has a fast access time like the main memory. But the flash memory must erase for recording and the erase cycle is limited. JFFS is a representative filesystem which reflects the characteristics of the flash memory. JFFS to be consisted of LSF structure, writes new data to the flash memory in sequential, which is not related to a file size. Mounting a filesystem or an error recovery is achieved through the sequential approach. Therefore, the mounting delay time is happened according to the file system size. This paper proposes a MJFFS to use a multi-checkpoint information to manage a mass flash file system efficiently. A MJFFS, which improves JFFS, divides a flash memory into the block for suitable to the block device, and stores file information of a checkpoint structure at fixed interval. Therefore mounting and error recovery processing reduce efficiently a number of filesystem access by collecting a smaller checkpoint information than capacity of actual files. A MJFFS will be suitable to a mobile device owing to accomplish fast mounting and error recovery using advantage of log foundation filesystem and overcoming defect of JFFS.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.258-260
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• 2003

In this paper, we study the reduction of the Dynamic False Contour in a new driving method. This method divides scan lines into Multi Blocks, and drives both selective write and selective erase address. Because of the characteristic of proposed waveform, each scan line has a different sustain pulse weight. Therefore, the Dynamic False Contour occurs seriously in the boundary of each Block. Finally, if scan-lines tie several lines, the Dynamic False Contour can reduce in the boundary of each Block.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.36-42
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• 2016

In multi-level-cell based storage devices, TLC NAND has been employed solid state drive due to cost effectiveness. Since TLC has slow performance and low endurance compared with MLC, TLC based storage has adopted SLC buffer scheme to improve performance. To improve SLC buffer scheme, this paper proposes page overwriting method in SLC block. This method provides data updates without erase operation within a limited number. When SLC buffer area is filled up, FTL should execute copying valid pages and erasing it. The proposed method reduces erase counts by 50% or more compared with previous SLC buffer scheme. Simulation results show that the proposed SLC buffer overwrite method achieves 2 times write performance improvement.

• Journal of Internet of Things and Convergence
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• v.8 no.5
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• pp.77-83
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• 2022

Nand flash memory requires an Erase-Before-Write operation structurally. In order to solve this problem, it can be solved by classifying a page (hot data page) where data update operation occurs frequently and storing it in a separate block. The MHF (Multi Hash Function Framework) technique records the frequency of data update requests in the system memory, and when the recorded value exceeds a certain standard, the data update request is judged as hot data. However, the method of simply counting only the frequency of the data update request has a limit in judging it as accurate hot data. In addition, in the case of a technique that determines the persistence of a data update request, the fact of the update request is recorded sequentially based on a time interval and then judged as hot data. In the case of such a persistence-based method, its implementation and operation are complicated, and there is a problem of inaccurate judgment if frequency is not considered in the update request. This paper proposes a lightweight hot data determination technique that considers both frequency and persistence in data update requests.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.175-178
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• 2008

While read operation on flash memory is fast and doesn't have any constraints, flash memory can not be overwritten on updating data, new data are updated in new area. If data are frequently updated, garbage collection, which is achieved by erasing blocks, should be performed to reclaim new area. Hence, because the number of erase operations is limited due to characteristics of flash memory, every block should be evenly written and erased. However, if data with access locality are processed by cost benefit algorithm with separation of hot block and cold block, though the performance of processing is high, wear-leveling is not even. In this paper, we propose CB-MG (Cost Benefit between Multi Group) algorithm in which hot data are allocated in one group and cold data in another group, and in which role of hot group and cold group is exchanged every period. Experimental results show that performance and wear-leveling of CB-MG provide better results than those of CB-S.