虛擬化環境與混合儲存裝置上之 檔案系統效能改進之研究

Abstract

近年來，現代的電腦系統所使用的資料儲存方式有兩個重大的改變：新儲存媒介的出現與虛擬化儲存裝置的興起。未來的檔案系統設計應該將兩個改變納入設計時的考量。為了因應這兩個改變，在本論文中，我們提出了兩個使用在檔案系統中的方法以提升在虛擬化環境與混合儲存裝置上的效能。首先對於新儲存媒介的出現，我們提出了一個具備高效能與兼具彈性的混合式檔案系統，稱為TridentFS，該檔案系統可以同時管理非揮發式記憶體、快閃記憶體與硬碟。TridentFS能夠善用這三個不同類型的儲存媒體以達到高效能資料儲存之目的。此外，相較於之前包含非揮發式記憶體的混合式檔案系統，TridentFS也能夠更有彈性的支援不同容量的非揮發式記憶體與不同格式的快閃記憶體。在虛擬化儲存裝置的興起的部分，我們提出了一個可以適用在虛擬機器中的日誌式檔案系統，稱為virtual machine aware journaling (VMA journaling) 。藉由與虛擬機器中的VMM的合作，VMA journaling能夠減少日誌式檔案系統為了維持檔案系統一致性與資料完整性所帶來的效能下降。 根據實驗結果顯示，當與將NVRAM以及由快閃記憶體與硬碟組合成的RAID-0比較時，TridentFS可以取得高達471.6%的效能改進。在虛擬化環境中，當與傳統的ext3日誌式檔案系統比較時，VMA journaling可以獲得高達50.9%的效能改進。

In recent years, there are two remarkable changes in data storage of modern computer systems, i.e., the emergence of new storage media and the rise of storage virtualization. Future file system design should consider these changes. In this thesis, we propose two approaches for these two changes. For the emergence of new storage media, we propose a hybrid file system called Trident file system (TridentFS). TridentFS is a hybrid file system aiming at achieving high performance and high flexibility. Three types of storages, i.e., NVRAM, flash memory and magnetic disk, are managed by TridentFS. The high performance is achieved by considering the storage characteristics. In addition, when compared with the previous NVRAM-based hybrid file system, TridentFS can support various forms of storage media and a wide range of NVRAM size. For the rise of storage virtualization, virtualized environments provide opportunities to file system to reduce the overhead of ensuring file system consistency and data integrity. We propose a novel journaling approach called virtual machine aware journaling (VMA journaling). VMA journaling can be used in most existing journaling file systems and can improve performance of the existing journaling file systems in virtualized environment. This is achieved by allowing cooperation between VMM and the journaling file systems. According the performance evaluation results, when comparing with RAID-0 which combines SSD and disk, TridentFS can achieves superior performance by up to 471.6%. VMA journaling achieves a performance improvement of up to 50.9% when compared with the traditional journaling approach of ext3.