基於Xen平台中實現DM-SCAN的硬碟I/O排程改善之研究

Implement DM-SCAN scheduling in Xen to improve disk I/O performance

陳英傑(Ying-Jie Chen)

指導教授 ： 石維寬

國立清華大學/電機資訊學院/資訊工程學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00076

摘要

近年來，雲端服務改變以往傳統網路服務的使用型態，雲端服務提供服務平台用於建立網路上的應用服務並由提供商來維護後端的服務主機，讓使用者不在需要額外花費成本與心力去維護服務的硬體平台，其中雲端服務所能發展的原因，虛擬化技術扮演了很重要的角色，虛擬化技術提供了在主機上同時運行多個虛擬系統的原理，讓這些虛擬系統可一同使用主機上的硬體資源，使硬體資源可以有效率的被使用，雲端服務可以透過租貸的方式提供這些虛擬系統給使用者進行使用，從而提高服務主機的收益並使得雲端服務得以發展。

然而在虛擬化技術中，虛擬系統都是同時共享著主機的硬體資源，也因此使得硬體使用效率會受到這些虛擬系統的運行受到干擾從而讓處理效率會有所降低，其中以硬碟I/O處理最為影響。而為了解決上述議題，有相關的研究提出了保證I/O處理量與滿足處理時間的排程，以改善系統對硬體的使用干擾性，但除了在虛擬化技術領域有所研究外，在多媒體領域上也有硬碟I/O處理的研究存在著，同時多媒體領域提出的硬碟I/O排程的概念與虛擬化技術提出的硬碟I/O排程有其相似存在，而這是否也意謂著前者的硬碟I/O排程也可以適用於虛擬化技術上使用。

因此，在本篇論文中，我們採用多媒體領域中的DM-SCAN排程實作在Xen虛擬平台中進行實驗，而實驗結果可得DM-SCAN排程在sequential讀取與random讀取測試中可以比EDF提高約5.1%與15.1%的提升，同時在提升硬碟I/O處理的情況下，也能比Deadline與Flubber改善近8成的miss deadline情況，另一方面，我們也在Xen中實作可用於控制虛擬系統的硬碟I/O的處理架構，並在實驗中可得該架構可以成功的控制虛擬系統的硬碟I/O處理量，完成在Xen可進行服務品質的機制。

關鍵字

虛擬化技術 ； Xen ； 硬碟排程 ； DM-SCAN ； 服務品質

並列摘要

Cloud Service changes the traditional service of internet in recent years. Cloud Service Provider provides user with service system to build the service. User does not care what hardware happened in the system, and only cares about the mantenance of service. The reason that cloud service can support user to build service is virtualization technology. It provides cloud service provider to create and manage multiple virtual system in one computer, and each system is isolated in computer. In this techology, Hardware can have the high Utilization in computer and also increase earnings for cloud service provider.

Virtualization technology improves the utilization of hardware in computer. However, it also cause the interference for each virtual system because virtual systems share the physical hardware. The interference can reduce the performance of hardware when all virtual system is high loading,ex: disk. To reduce the interference of disk, some researches provides the solution to improve throughput and latency for disk and virtual system. On the other hand, there are also some solution to improve throughput and latency for disk in multimedia systems. To compare with solutions in virtualization technology, some idea are similar for improving the throughput with disk. It also means whether or not solution in multimedia can be used in virtualization technology.

In this paper, we implement DM-SCAN scheduling for multimedia in Xen virtualization platform. We compare the throughput and latency with EDF, Deadline, and Flubber. DM-SCAN can improve 5.1% and 15.1% throughput in sequential read and random read which compared with EDF. Therefore, In low deadline setting, DM-SCAN can improve the amount of miss deadline compared with Deadline and Flubber. It means DM-SCAN can be used in Xen and has the better improvement in disk interference.

並列關鍵字

Virtualization Technology ； Xen ； Disk I/O Scheduling ； DM-SCAN ； Quality of Service

參考文獻

[1]. Ray-I Chang, Wei-Kuan Shih, and Ruei-Chuan Chang. Real-Time Disk Scheduling for Multimedia Applications with Deadline-Modification-Scan Scheme. Real-Time Systems, Volume 19 Issue 2, Page 149-168, 2000.

[25]. Jianyong Zhang, Anand Sivasubramaniam, et al. Storage Performance Virtualization via Throughput and Latency Control. ACM Transactions on Storage, Volume 2 Issue 3, Pages 283-308, ACM, 2006.

[26]. Hai Jin, Xiao Ling, Shadi Ibrahim, et al. Flubber: Two-level Disk Scheduling in Virtualized Environment. Future Generation Computer Systems, Volume 29 Issue 8, Pages 2222-2238, 2013.

[27]. Ajay Gulati, Arif Merchant, Mustafa Uysal, et al. Efficient and adaptive proportional share I/O scheduling. Technical Report HPL-2007-186, HP Labs, 2007.

[28]. P. Valente and F. Checconi. High throughput disk scheduling with fair bandwidth distribution. IEEE Transactions on Computers, Volume 59 Issue 9, Pages 1172-1176, IEEE, 2010.