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Michail D. Flouris

Michail D. Flouris
OnApp Ltd., UK · Emerging Technologies Group

Ph.D. in Computer Science

About

40
Publications
8,236
Reads
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441
Citations
Additional affiliations
February 2012 - present
OnApp Limited, UK
Position
  • Researcher & Software Architect
May 2007 - June 2011
Foundation for Research and Technology - Hellas
Position
  • Collaborating Researcher
September 2000 - August 2007
University of Toronto
Position
  • PhD Student
Education
September 2000 - January 2009
University of Toronto
Field of study
  • Computer Science

Publications

Publications (40)
Chapter
Modern NVMe Flash devices deliver over 1 million random I/O operations per second (IOPS) at sub‐100 µs latencies, making them orders of magnitude faster than traditional hard drives with rotating disks, especially for random I/O. In this chapter, the authors explain the challenges of high‐performance cloud computing, especially with respect to stor...
Conference Paper
Full-text available
Platform-As-A-Service (PaaS) systems offer customers a rich environment in which to build, deploy, and run applications. Today's PaaS offerings are tailored mainly to the needs of web and mobile applications developers, and involve a fairly rigid stack of components and features. The vision of the H2020 5GPPP Phase 2 Next Generation Platform-as-a-S...
Conference Paper
Full-text available
Despite their proliferation as a dominant computing paradigm, cloud computing systems lack effective mechanisms to manage their vast amounts of resources efficiently. Resources are stranded and fragmented, ultimately limiting cloud systems' applicability to large classes of critical applications that pose non-moderate resource demands. Eliminating...
Research
Full-text available
Virtualization of server hardware is a commonly used practice to provide scalable resource management. In order to meet a variety of emerging technology trends, a novel, super-lightweight Type I Hypervisor architecture is essential. The proposed ‘Microvisor’ architecture is significant for a number of reasons. 1. Resource utilization efficiency. Mi...
Article
Full-text available
In this work, we examine how transparent block-level compression in the I/O path can improve both the space efficiency and performance of online storage. We present ZBD, a block-layer driver that transparently compresses and decompresses data as they flow between the file-system and storage devices. Our system provides support for variable-size blo...
Conference Paper
Full-text available
Flash-based solid state drives (SSDs) exhibit potential for solving I/O bottlenecks by offering superior performance over hard disks for several workloads. In this work we design Azor, an SSD-based I/O cache that operates at the block-level and is transparent to existing applications, such as databases. Our design provides various choices for assoc...
Conference Paper
Full-text available
As the number of user-managed devices continues to increase, the need for synchronizing multiple file hierarchies distributed over devices with ad hoc connectivity, is becoming a significant problem. In this paper, we propose a new approach for efficient cloud-based synchronization of an arbitrary number of distributed file system hierarchies. Our...
Article
High-performance storage systems are evolving towards decentralized commodity clusters that can scale in capacity, processing power, and network throughput. Building such systems requires: (a) Sharing physical resources among applications; (b) Sharing data among applications; (c) Allowing customized data views. Current solutions typically satisfy t...
Conference Paper
In this work we examine how transparent compression in the I/O path can improve space efficiency for online storage. We extend the block layer with the ability to compress and decompress data as they flow between the file-system and the disk. Achieving transparent compression requires extensive metadata management for dealing with variable block si...
Conference Paper
Full-text available
Flash-based solid state drives (SSDs) offer superior performance over hard disks for many workloads. A prominent use of SSDs in modern storage systems is to use these devices as a cache in the I/O path. In this work, we examine how transparent, online I/O compression can be used to increase the capacity of SSD-based caches, thus increasing the cost...
Conference Paper
Full-text available
Retrieving sequential rich media content from modern commodity disks is a challenging task. As disk capacity increases, there is a need to increase the number of streams that are allocated to each disk. However, when multiple streams are accessing a single disk, throughput is dramati- cally reduced because of disk head seek overhead, resulting in r...
Conference Paper
Full-text available
High-performance storage systems are evolving towards decentralized commodity clusters that can scale in capacity, processing power, and network throughput. Building such systems requires: (a)Sharing physical resources among applications; (b)Sharing data among applications; (c) Allowing customized views of data for applications. Current solutions s...
Chapter
Full-text available
The Data Grid is becoming a new paradigm for eHealth systems due to its enormous storage potential using decentralized resources managed by different organizations. The storage capabilities in these novel “Health Grids” are quite suitable for the requirements of systems like ICGrid, which captures, stores and manages data and metadata from Intensiv...
Article
Full-text available
High-performance storage systems are evolving from centralized architectures and specialized hardware to "storage bricks", i.e. a large set of decentralized commodity components with more processing power and network throughput. These emerging systems offer increased flexibility for tailoring storage to application needs. In this paper, we present...
Conference Paper
Full-text available
Volunteer computing is becoming a new paradigm not only for the computational grid, but also for institutions using production-level data grids because of the enormous storage potential that may be achieved at a low cost by using commodity hardware within their own computing premises. However, this novel "Desktop Data Grid" depends on a set of wide...
Conference Paper
Storage capabilities in novel "Health Grids" are quite suitable for the require- ments of systems like ICGrid, which captures, stores and manages data and metadata from Intensive Care Units. However, this paradigm depends on widely distributed storage sites, therefore requiring new security mechanisms, able to avoid potential leaks to cope with mod...
Conference Paper
Scalable and cost-effective Storage Elements are essentia l components of Grid systems. An increasing number of data-intensive applications and services in Grids make the cost-effective scalability of capacity and performance of the storage infrastructure a very hot research topic. In this pa per, we present the practical evaluation of the performa...
Chapter
Full-text available
With the wide-spread deployment of Data Grids, storage services are becoming a critical aspect of the Grid infrastructure. Due to the sensitive and critical nature of the data being stored, security issues related with state of the art data storage services need to be studied thoroughly to identify potential vulnerabilities and attack vectors. In t...
Chapter
Full-text available
Storage elements that can scale to large capacities and high-performance are an essential component of future GRID infrastructures, especially for supporting an increasing number of data-intensive applications and services. This paper studies two approaches for building scalable networked storage elements: enterpriselevel, Fibre-Channel-based Stora...
Article
Full-text available
Storage capabilities in novel "Health Grids" are quite suitable for the require- ments of systems like ICGrid, which captures, stores and manages data and metadata from Intensive Care Units. However, this paradigm depends on widely distributed storage sites, therefore requiring new security mechanisms, able to avoid potential leaks to cope with mod...
Chapter
The quality of virtualization mechanisms provided by a storage system affects storage management complexity and storage efficiency, both of which are important problems of modern storage systems. We argue that current storage systems provide limited flexibility and extensibility in virtualizing, managing and accessing storage. In this work we addre...
Chapter
Full-text available
Scalable storage systems are expected to scale to large numbers of physical storage devices and to service diverse applications without incuring high management costs. New storage virtualization architectures and techniques that are currently being proposed, aim at addressing these needs by providing the ability to configure storage systems to meet...
Conference Paper
Full-text available
Distributed storage systems are expected to serve a broad spectrum of applications, satisfying various requirements with respect to capacity, speed, reliability, security at low cost. Virtualization techniques allow flexible configuration of storage systems in order to meet resource constraints and application requirements. Violin provides block le...
Conference Paper
Full-text available
To satisfy current and future application needs in a cost effective manner, storage systems are evolving from mono- lithic disk arrays to networked storage architectures based on commodity components. So far, this architectural transi- tion has mostly been envisioned as a way to scale capacity and performance. In this work we examine how the block-...
Conference Paper
In this paper, we present our vision on building large-scale storage systems from commodity components in a data center. For reasons of efficiency and flexibility, we advocate maintaining sophisticated data management functions behind a block-based interface. We anticipate that such an interface can be customized to meet the diverse needs of end-us...
Conference Paper
Full-text available
In this paper, we present our vision on building large-scale storage systems from commodity components in a data center. For reasons of efficiency and flexibility, we advocate maintaining so-phisticated data management functions behind a block-based in-terface. We anticipate that such an interface can be customized to meet the diverse needs of end-...
Conference Paper
Full-text available
iSCSI is proposed as a possible solution to building future stor- age systems. However, using iSCSI raises numerous questions about its implications on system performance. This lack of un- derstanding of system I/O behavior in modern and future systems inhibits providing solutions at the architectural and system levels. Our main goals in this work...
Conference Paper
Full-text available
In this work we propose Violin, a virtualization framework that allows easy extensions of block-level storage stacks. Violin allows (i) developers to provide new virtualization functions and (ii) storage administrators to combine these functions in storage hierarchies with rich semantics. Violin makes it easy to develop such new functions by provid...
Article
When evaluating the performance of commercial work- loads it is important to be able to examine overheads induced by the operating system kernel. Currently the only method for understanding kernel overheads is by using sample-based profiling tools. Although profiling can be very useful, one of its main limitations is that it does not allow the prec...
Article
Full-text available
Recently storage management has emerged as one of the main problems in building cost effective storage infrastructures. One of the issues that contribute to management complexity of storage systems is maintaining previous versions of data. Up till now such functionality has been implemented by high-level applications or at the filesystem level. How...
Article
Full-text available
this paper, when we mention the Lambek Calculus (LC) or Lambek Grammars (LG), we are referring to the product-free fragment
Article
this paper, when we mention the Lambek Calculus (LC) or Lambek Grammars (LG), we are referring to the product-free fragment
Article
Full-text available
Many proxy servers that run on today's computers are limited by their file I/O needs. Even if the proxy is configured with sufficient I/O hardware, the file system software often fails to provide the available bandwidth to the proxy processes. Although specialized file systems may offer a significant improvement and overcome these limitations, we b...
Article
Full-text available
World-Wide Web proxies are being increasingly used to provide Internet access to users behind a firewall and to reduce wide-area network traffic. Recent results suggest that disk I/O is increasingly becoming the limiting factor for the performance of web proxies. In this paper we study the overheads associated with disk I/O for web proxies, and pro...
Article
Full-text available
Efficient data storage, a major concern in the modern computer industry, is mostly provided today by traditional magnetic disks. However, the cost of a disk transfer (measured in processor cycles) continues to increase with time, making disk accesses increasingly expensive. In this paper we describe the design, implementation and evaluation of a Ne...
Conference Paper
Full-text available
World-Wide Web proxies are being increasingly used to provide Internet access to users behind a firewall and to reduce wide-area network traffic. Recent results suggest that disk I/O is increasingly becoming the limiting factor for the performance of web proxies. In this paper we study the overheads associated with disk I/O for web proxies, and pro...
Article
The quality of service (QoS) problem of the World Wide Web and the protection of intranets behind firewalls, lead to the increasing use of WWW Proxies (or WWW Caches) as the only long-term solution. However, due to the exponential growth of the Web, there is an increasing demand for higher performance WWW Proxies with larger WWW object caches, not...

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Projects

Project (1)
Project
ACTiCLOUD’s vision is to develop a novel cloud architecture that will break the existing scale-up and share-nothing barriers and enable the holistic management of physical resources both at the local cloud site and the distributed levels, targeting drastically improved utilization and scalability of resources. This will ultimately translate to: a) significant cost and performance improvements for CSPs, b) higher performance stability and lower pricing for cloud applications, and c) enhanced flexibility and scalability of cloud resources for intensive database applications that have until now faced tough challenges in covering their resource demands from existing cloud offerings.