Applying Content-Defined Chunking to OCSSD-based Deduplication Systems

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Title:	Applying Content-Defined Chunking to OCSSD-based Deduplication Systems
Authors:	陳哲民;Chen, Che-Min
Contributors:	資訊工程學系
Keywords:	快閃記憶體;固態硬碟;內容定義分塊;重複資料刪除技術;NAND Flash;Solid State Drives;Content-Defined Chunking;Data Deduplication
Date:	2023-08-11
Issue Date:	2024-09-19 17:02:37 (UTC+8)
Publisher:	國立中央大學
Abstract:	本文探討了將內容定義分塊 (Content-Defined Chunking, CDC) 技術應用於基於固態硬碟(Solid State Drive, SSD) 的重複資料刪除系統(Data Deduplication System)上所遭遇得挑戰與機會。CDC 是一種根據資料的內容，而非根據邏輯位址，將資料分割成不特定長度的分塊的技術。CDC 可以減少寫入儲存系統的重複資料量，從而提高 SSD 的效能和儲存效率。然而，CDC 也為基於 SSD 的重複資料刪除系統帶來了一些難題，例如分塊與 SSD 頁面之間的不對齊，以及邏輯區塊位址 (LBAs) 與實體頁面位址 (PPAs) 之間的低效率位址映射。為了解決這些問題，我們提出了利用主機管理型 SSD (例如 OCSSD、ZNS) 的方法，這是一種新型的 SSD，它將其內部區塊暴露給主機系統，並允許主機系統完全控制 SSD 內的資料放置。我們提出了一種簡單的資料對齊技術，以減輕不對齊對讀取效能的負面影響。我們還結合了多重串流 (multi-streaming) 的概念，根據資料的壽命將其分配到不同的串流中，並利用主機提供的關於分塊大小和創建時間的資訊，以實現更好的資料放置和減少垃圾收集的花費。我們用模擬實作的方式來評估我們提出的方法，並分享一些關於我們所遭遇得挑戰的見解。;This paper explores the challenges and opportunities of applying Content-Defined Chunking (CDC) to SSD-based deduplication systems. CDC is a technique that divides data into variable-sized chunks based on their content, rather than fixed-sized blocks based on their logical addresses. CDC can reduce the amount of redundant data written to the storage system, which can improve the performance and storage efficiency of SSDs. However, CDC also introduces some difficulties for SSD-based deduplication systems, such as misalignment between chunks and SSD pages, and inefficient address mapping between logical block addresses (LBAs) and physical page addresses (PPAs). To address these issues, we propose to leverage host-managed SSDs (e.g. OCSSD, ZNS), a new type of SSDs that that expose their internal blocks to the host system and allow the host system to to fully control the data placement within the SSD. We proposed a simple data fitting technique to alleviate the negative impact of misalignment on read performance. We also combine the concept of multi-streaming, which distribute data based on lifetime into different streams, with the host-provided information about chunk′s size and creation time, to achieve better data placement and mitigate the overhead of garbage collection, and. We evaluate our approach with a simulated implementation and share some insights of the challenges.
Appears in Collections:	[Graduate Institute of Computer Science and Information Engineering] Electronic Thesis & Dissertation

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