PhD Thesis Proposal Announcement

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Title: Enhancing Storage Performance in Virtualized Environments: A Pro-active Approach

Sankaran Sivathanu
School of Computer Science
Georgia Institute of Technology

Committee :
Dr. Ling Liu (Professor, School of CS, Georgia Tech)  [Advisor]
Dr. Calton Pu (Professor, School of CS, Georgia Tech)
Dr. Umakishore Ramachandran (Professor, School of CS, Georgia Tech)
Dr. Shamkant Navathe (Professor, School of CS, Georgia Tech)

Virtualization of computer resources is widely recognized as an important revolution in computing industry over the last decade. Virtualization technology provides some unique opportunity for better resource utilization and more effective server and application consolidation.  While CPU, memory and network virtualization have been studied in depth in the research community, the impact of virtualization on storage systems has not been analyzed in depth and understood completely. We argue that certain I/O functions that were traditionally the responsibility of file systems become sub-optimal in the virtual machine context because a physical resource is typically shared across multiple operating domains. In this dissertation, we present a pro-active approach to storage performance enhancement in virtualized cloud computing environments.

This dissertation research makes three unique contributions.   First, we analyze the effect of system virtualization on storage performance through a variety of experiments. We identify the set of storage system parameters that are critical to storage performance in virtualized cloud environments. We examine how each individual virtual machine contends for the physical storage by running different kind of workload combinations under different resource allocations in the individual virtual machines. We make interesting observations from these experiments that shed more light on the problems to be addressed in order to achieve good storage performance in a virtualized computing environment. The information divide in the virtual machine world is an instance of a more general issue of functionality placement between the lower I/O layers and the file system. To enable better co-operation in functionality between the layers of the I/O stack, the second contribution we make in this dissertation research is to introduce the notion of Pro-active Disks, which represents a novel mode of interaction between storage systems and higher layers of the storage stack such as file systems. Instead of viewing the storage system as a passive entity in the storage stack that simply responds to higher level requests, we propose a model where the disk can pro-actively and opportunistically initiate requests on the higher layers. We show that the proactive capability of initiating requests on the higher storage layer offers a unique advantage: It enables exploiting internal information specific to the storage system to optimize higher level policies without the higher layer needing to know the details of the storage-level information. Finally, we develop an evaluation framework consisting of a block-level I/O trace replay tool. A salient feature of this development is being ‘context-aware’ in the sense that the trace replay can adjust itself according to the system in which it is replayed, instead of plainly following the original trace characteristics.

In this dissertation proposal exam, I will give an overview of our proactive approach to storage performance optimization, focusing on addressing the following two questions: (I) how does the system virtualization impact on the performance of storage systems, and (ii) what opportunities do the proactive disk approach offer in terms of storage management and storage performance optimization. We end the talk by providing a summary of our ongoing research that extends the architecture of Pro-active Disks in virtualized environments and leverage additional opportunities that are specific to virtualized systems.  We also plan to modify our context aware I/O trace replay framework to account for extra layering delays introduced by virtualization, in order to use it to evaluate the concept of Pro-active Disks in virtualized environments.


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    Cristina Gonzalez
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