隨著不同的儲存技術被發展出來，固態硬碟已經是目前備受矚目的儲存裝置，而固態硬碟是由快閃記憶體所構成的產品，不僅擁有高耐震性與高效能等特色，且隨者硬體的成本越來越低，普及性也變得越來越高，許多關於固態硬碟的研究也越來越多。現在更有把固態硬碟作為虛擬儲存裝置的想法出現,雖然固態硬碟的在讀寫效能上表現很好，但快閃記憶體會有垃圾回收的動作出現，當有多個使用者的應用程式跑在上面，將會出現使用者行為受到其他使用者干擾的情況，如此一來會無法在虛擬儲存裝置下達到效能獨立的特性。
而VSSD的出現,達到了效能隔離的功效，將使用者所使用的空間獨立開來，每一個塊都只有一個使用者所擁有，不會有共用的情形發生，另外在觸發垃圾回收的時候也只會挑選屬於自己使用的塊作為犧牲塊來清出空間。但VSSD為了達到效能隔離的目的，使用者之間的空間是無法共用的，如此會導致空間利用率較低的情形。本篇論文是建立在VSSD的架構上做修改達到有效的空間利用，動態判斷各個使用者的空間使用情形，並藉由空間的借取與歸還來達到效能提升並維持效能隔離。

With different storage technologies are developed, solid state drive is already the highly anticipated storage devices, and solid state drives are the product posed by the flash memory, not only has a high shock resistance but also has high performance. With hardware costs by getting low, are becoming increasingly high popularity, many studies on the solid state drive is also increasing. The idea about the solid state drive appearing as a virtual storage device now is more and more, although the SSD write performance is very excellent, but the flash memory will trigger garbage collection action when space is lower than some threshold. If there are multiple user applications run at SSD, there will be cases of interference user behavior by other users, in this way, it will not achieve the performance isolation characteristics under a separate virtual storage device.
The emergence of VSSD reached the performance isolation, the space used by the user is independent, each block belongs to one user, and the space could not be shared to other user. Moreover, when the garbage collection is triggered, the system picks a victim block to free up space from its own space. However, in order to achieve the performance isolation, the space could not be shared between users, then result in a scenario of lower space utilization. This paper is based on VSSD structure that can achieve efficient space utilization. Dynamically detect space condition of used for each user and by the mechanism of lend and return of space to achieve performance improvement and maintain the performance isolation.

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