• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3583-3598
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• 2019

In order to improve the reliability and repair efficiency of distributed storage systems, minimum bandwidth regenerating (MBR) codes based on cyclic variable fractional repetition (VFR) codes are constructed in this thesis, which can repair failed nodes accurately. Specifically, in order to consider the imbalance of data accessed by the users, cyclic VFR codes are constructed according to that data with different heat degrees are copied in different repetition degrees. Moreover, we divide the storage nodes into groups, and construct MBR codes based on cyclic VFR codes to improve the file download speed. Performance analysis and simulation results show that, the repair locality of a single node failure is always 2 when MBR codes based on cyclic VFR codes are adopted in distributed storage systems, which is obviously superior to the traditional MBR codes. Compared with RS codes and simple regenerating codes, the proposed MBR codes based on cyclic VFR codes have lower repair locality, repair complexity and bandwidth overhead, as well as higher repair efficiency. Moreover, relative to FR codes, the MBR codes based on cyclic VFR codes can be applicable to more storage systems.

• ETRI Journal
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• 제38권3호
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• pp.529-539
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• 2016

Recently, a product-matrix (PM) framework was proposed to construct optimal regenerating codes for homogeneous distributed storage systems (DSSs). In this paper, we propose an extended PM (EPM) framework for coding of heterogeneous DSSs having different repair bandwidths but identical storage capacities. Based on the EPM framework, an explicit construction of minimum remote-repair bandwidth regenerating (MRBR) codes is presented for a specific heterogeneous DSS, where two geographically different datacenters with associated storage nodes are deployed. The data reconstruction and regeneration properties of the MRBR code are proved strictly. For the purpose of demonstration, an example implementation of MRBR code is provided. The presented MRBR code is the first optimal strict-regenerating code for heterogeneous DSSs. In addition, our proposed EPM framework can be applied to homogeneous systems also.

• 한국통신학회논문지
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• 제41권12호
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• pp.1684-1691
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• 2016

최근 분산 저장 시스템에 erasure code를 활용하여 저장소 효율성을 높이려는 연구가 활발히 진행되고 있다. 재생 부호(regenerating codes)는 erasure code의 일종으로, 높은 저장소 효율성과 네트워크 효율성을 가지는 코드이다. (n,k,d)-재생 부호는 n개의 저장소 노드를 가지며, 손실된 노드가 발생하였을 때, 해당 노드는 d개의 살아남은 노드로부터 정보를 다운로드받아 복구될 수 있다. 하지만 일반적인 재생 부호는 노드 복구 시 정확히 d개의 도움 노드들을 사용해야 하며, 노드 손실이 빈번하거나, 노드 간 접속이 불안정한 환경에서, d개 이하의 노드들에만 접속 가능할 경우에 유연하게 대처할 수 없다. 본 논문에서는 약간의 복구 대역폭의 희생을 통하여, $$k{\leq_-}{\bar{d}}{\leq_-}d$$의 다양한 도움 노드의 수 ${\bar{d}}$개로 노드를 복구할 수 있는 유연한 코드 운용 방식을 제안하였다.