【摘要】：基于NAND Flash的固態(tài)盤憑借其低能耗、低故障率、高性能等優(yōu)勢,正逐步應(yīng)用到企業(yè)級服務(wù)器和高性能計算領(lǐng)域。為保持主機對固態(tài)盤的訪問接口與磁盤兼容,并有效解決NAND Flash的重寫前擦除和擦除次數(shù)有限等固有特性引起的各類問題,提高固態(tài)盤的整體性能,固態(tài)盤在文件系統(tǒng)和NAND Flash之間引入閃存轉(zhuǎn)換層,以處理地址映射、垃圾回收和磨損均衡等問題。其中,地址映射將請求的邏輯地址映射為固態(tài)盤內(nèi)物理地址,根據(jù)映射粒度的不同可分為頁映射、塊映射和混合映射。頁映射方式存在映射表過大的問題,限制了其在固態(tài)盤中的實際應(yīng)用。當(dāng)前主流的DFTL算法在頁映射的基礎(chǔ)上選擇性地緩存最近常用的頁映射關(guān)系,一定程度上緩解了頁映射表過大的問題,但因映射信息未命中緩存而產(chǎn)生的額外開銷嚴重影響了固態(tài)盤的整體性能。針對上述問題,本文提出了一種有效利用負載時空局部性的地址映射方法ECAM,ECAM將多個物理頁號和邏輯頁號均連續(xù)的頁映射關(guān)系用一條帶有SIZE域的地址映射關(guān)系表示,并在對頁映射信息的緩存管理策略中賦予SIZE值較大的地址映射信息更高的優(yōu)先級。ECAM根據(jù)負載的局部性原理對緩存內(nèi)地址映射信息進行管理,在緩存空間一定的情況下緩存更多有用的地址映射信息,提高緩存命中率,減少緩存失效產(chǎn)生的額外讀寫操作,提高固態(tài)盤整體性能。同時,針對NAND Flash讀寫性能與負載特性相關(guān)的特點,本文在ECAM基礎(chǔ)上提出了一種基于負載預(yù)測的自適應(yīng)閃存轉(zhuǎn)換層算法WAPFTL。WAPFTL通過對負載特征的預(yù)測動態(tài)調(diào)整緩存管理策略,避免緩存隨機寫請求的地址映射信息時造成的空間浪費,在各類負載下提高有限空間緩存的命中率,進一步提高固態(tài)盤整體性能。測試結(jié)果表明本文提出的ECAM和WAPFTL可以有效提高地址映射信息的緩存命中率,減少緩存未命中而產(chǎn)生的額外開銷,有效提高固態(tài)盤的整體性能。
[Abstract]:With the advantages of low energy consumption, low failure rate and high performance, solid state disk based on NAND Flash is gradually applied to enterprise server and high performance computing field. In order to keep the host's access interface to the solid disk compatible with the disk, and to effectively solve all kinds of problems caused by the inherent characteristics of NAND Flash, such as erasing before rewriting and limited erasure times, the overall performance of the solid state disk can be improved. Flash transfer layer is introduced between file system and NAND Flash to deal with address mapping, garbage collection and wear balance. Address mapping maps the requested logical addresses to solid-state in-disk physical addresses, which can be divided into page mapping, block mapping and hybrid mapping according to the mapping granularity. The problem of large mapping table in page mapping mode limits its practical application in solid-state disk. The current mainstream DFTL algorithm selectively caches the recently commonly used page mapping relationships on the basis of page mapping, which to some extent alleviates the problem of excessive page mapping. However, the additional overhead caused by the missed cache of mapping information seriously affects the overall performance of the solid-state disk. In order to solve the above problems, this paper presents an effective address mapping method based on the spatio-temporal localization of load, ECAM,ECAM, which represents multiple physical page numbers and logical page numbers as an address mapping relation with SIZE domain. In the cache management strategy of page mapping information, the address mapping information with larger SIZE value is given higher priority. ECAM manages the address mapping information in the cache according to the local principle of load. In the case of fixed cache space, more useful address mapping information is cached, the cache hit rate is improved, the additional read and write operations caused by cache failure are reduced, and the overall performance of solid state disk is improved. At the same time, according to the characteristics of NAND Flash read and write performance and load characteristics, this paper proposes an adaptive flash conversion layer algorithm based on load prediction based on ECAM, WAPFTL.WAPFTL dynamically adjusts buffer management strategy by predicting load characteristics. It avoids the space waste caused by caching the address mapping information of random write requests, improves the hit rate of limited space cache under various loads, and further improves the overall performance of solid-state disk. The test results show that the proposed ECAM and WAPFTL can effectively improve the cache hit rate of address mapping information, reduce the extra overhead caused by cache miss, and effectively improve the overall performance of solid-state disk.
【學(xué)位授予單位】：國防科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TP333
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本文編號：2278538