隨著科技的發展，人們創造的資料量連年提升，且近年來資料儲存方式多已
數位化，大量儲存系統也隨之蓬勃發展，無論是雲端技術或各類型data center 皆
需要使用多個儲存設備，這樣的儲存系統需要大量的供電，這些耗電量不僅減少
了企業的營收，也讓能源損耗得更為嚴重，因此如何減少大量儲存系統的用電量，
已成為重要的議題。
節約能源的做法，在傳統上是希望能使硬碟有效率的spin-down，因為儲存
系統中的閒置模式或是睡眠模式往往會被使用者的要求(request)被迫中斷，因而
進入耗電的存取模式，因此應盡量延長硬碟閒置的時間以達成節電。為了使研究
貼近實際資料存取模式(access pattern)，我們分析了各種實際系統的workload，
觀察這些workload 後，得知實際系統中大部分資料存在批次讀寫的特性。因此
應用SSD 結合硬碟作為儲存系統，將SSD 做為buffer 以暫存資料的方式，並根
據workload 特性訂定寫入機制(write policy)讓資料得以有效率的批次寫入硬碟，
達成減少電能的損耗，此外也制定讀取機制(read policy)作為系統上的微調。
另外，如何確保不遺失資料使資料具有可靠性也是我們考量的議題，我們參
考了幾種容錯機制，並作仔細的分析，將其中一種容錯機制經由調整演算法後納
入所提出的系統，因此我們結合了資料容錯與節約能源兩方向的議題做研究。
我們主要的挑戰在於資料的可靠度需要以空間換取，例如增加冗餘位元，而
這些存放資料與冗餘位元的空間可能讓系統更耗電，因此如何藉由資料放置的方
法使系統在資料可靠度與能源耗損兩者中取得最大效益，又能讓機制擁有足夠的
動態調整性能，讓省電機制在不同的workload 也能發揮效益，這是我們所挑戰
的目標。而我們系統的實驗結果達成20%~40%的省電量。

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