在高效能的分散式系統中, 經常藉由複製常被存取的檔案以減少擁有這些檔案的節點的工作量. 傳統複製檔案的演算法大多依靠分析 client 存取行為的記錄檔來決定要將檔案複製於那些節點內. 在這篇論文中, 我們提出了 LessLog, 一個不需要分析 client 記錄檔的演算法, 是為了結構式點對點分散式系統 (structured peer-to-peer system) 所設計的. 在這個演算法中, 我們利用 binomial tree, 首先建構出一顆唯一的 virtual replication tree.
再用此 virtual replication tree 經過一些運算後, 得到 N 顆不同的 physical replication trees. 並利用 physical replication tree, 來決定檔案要被複製於那個節點. LessLog 使用位元運算 (bitwise operations) 來決定複製的檔案要擺放到那一個節點, 同時這個過程並不需要分析任何 client 的記錄檔, 也因此, LessLog 的演算法非常簡單, 且有效率. 除此之外, 每一個複製的檔案都保證能減少原來擁有這個檔案的節點約 1/2 的工作量. 最後, 我們也提供了具有容錯性的 LessLog. 在這個模型中, 我們考慮了在點對點系統裡, 若有節點 i 意外的離開系統時, LessLog 仍然能保證當使用者想要存取原本存在於節點 i
的檔案, 仍然能在其他節點尋找到, 並被成功的存取. 同時, LessLog 也允許節點動態的加入或離開系統.
實驗結果顯示 LessLog 與最簡單的隨機複製檔案的方法,
或需要分析使用者存取記錄的方法比起來,
LessLog 只需使用很少的 replicas, 就能成功且有效的減少原本負擔過重的節點的工作量.

The technique of replicating frequently-accessed files to other nodes has been widely used in a high-performance distributed system to reduce the load of the nodes hosting these files. Traditional file replication algorithms rely on the analysis of client-access logs to determine the location of the replicated nodes. In this paper, we present LessLog, a logless file replication algorithm, developed for a peer-to-peer distributed system. We first construct a replication tree for each node. LessLog uses bitwise operations to determine the location of the replicated node without any client-access history. In addition, each replication is guaranteed to reduce the workload of the replicating node by half. A fault-tolerant LessLog model is also presented. The experimental results show that LessLog
successfully and e±ciently reduces the load of overloaded nodes.

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