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Service providers hosting multi-tiered applications require accurate analytical models of the applications they will host for different system management activities, such as capacity planning, configuration management, cost analysis and feedback control. Due to the complexity of real world scenarios, developing accurate analytical models is hard. This paper presents the commonly faced challenges in...
The design of evolving discrete-event systems needs for adequate modeling techniques. A Petri net-based reflective layout has been recently proposed to support dynamic discrete event system's design. Keeping functional aspects separated from evolutionary ones, deploying changes to the (current) system configuration when necessary, results in a clean formal model preserving the ability of verifying...
Requests scheduling in Web servers is a hot research topic. Many works aim at providing optimal algorithms according to various metrics. Most of these works are based on classical scheduling metrics, considering jobs completion times, but ignoring intermediate states. We claim that this choice conduces to the design of algorithm that do not efficiently share the system resources. Indeed, Web servers...
Flash memory has become increasingly popular in today's storage systems. However, replacing hard drives with flash memory in current systems often either requires major file system changes or causes performance degradation due to the limitations of block-based interface and out-of-place updates required by flash. To alleviate this problem, we propose an object-based model for flash memory that gives...
To reduce cloud system resource cost, application consolidation is a must. In this paper, we present a novel pattern driven application consolidation (PAC) system to achieve efficient resource sharing in virtualized cloud computing infrastructures. PAC employs signal processing techniques to dynamically discover significant patterns called signatures of different applications and hosts. PAC then performs...
Currently implemented Spanning Tree Protocol (STP) cannot meet the requirement of a data center due to its poor bandwidth utilization and lack of multipathing capability. In this paper, we propose a layer-2 multipathing solution, namely dynamic load balancing multipathing (DLBMP), for data center Ethernets. With DLBMP, traffic between two communication nodes can be spread among multiple paths. The...
We present Barra, a simulator of Graphics Processing Units (GPU) tuned for general purpose processing (GPGPU). It is based on the UNISIM framework and it simulates the native instruction set of the Tesla architecture at the functional level. The inputs are CUDA executables produced by NVIDIA tools. No alterations are needed to perform simulations. As it uses parallelism, Barra generates detailed statistics...
Multi-core trends are becoming dominant, creating sophisticated and complicated cache structures. Also, the bigger shared level-2 (L2) caches are demanded for higher cache performance. One of the easiest ways to design cache memory for increased performance is to double the cache size. However, the big cache size is directly related to the area and power consumption. Especially in mobile processors,...
We consider the problem of optimal cluster-based data gathering in Wireless Sensor Networks (WSNs) when nearby readings are spatially correlated. Due to the dense nature of WSNs, data samples taken from nearby locations are statistically similar. We show how this data correlation can be exploited to reduce the amount of data to be transmitted in the network and thus conserve energy. While much attention...
Archer is a simulation environment and computing resource for research in the field of computer architecture. Archer facilitates the creation of an on-demand computing grid, the deployment of simulation tools on this grid and the batch scheduling of large-scale simulation jobs on this grid. These features enable the use of Archer for simulation-based research as well as dissemination of tools and...
Secondary storage devices have become increasingly vulnerable to security attacks as they are now accessed remotely, attached to mobile devices, or used in other previously unanticipated operating environments. Storage vendors have responded to this by offering solutions that encrypt data on the fly-in software or device firmware-before recording. The performance versus security trade-off offered...
The design and the requirements of modern computer-based systems have reached a complexity level that calls for the use of models for the verification of non functional requirements since the beginning of their design cycle. Such systems are however too complex to be modeled directly in a simple unstructured formal language like Queueing Networks or Petri Nets. SIMTHESys (Structured Infrastructure...
We present two new cooperative caching algorithms that allow a cluster of file system clients to cache chunks of files instead of directly accessing them from origin file servers. The first algorithm, called C-LRU (Cooperative-LRU), is based on the simple D-LRU (Distributed-LRU) algorithm, but moves a chunk's position closer to the tail of its local LRU list when the number of copies of the chunk...
Mobility models have traditionally been tailored to specific application domains such as human, military, or ad hoc transportation scenarios. This tailored approach often renders a mobility model useless when the application domain changes, and leads to wrong conclusions about the performance of protocols and applications running atop of different domains. In this work we propose and implement a mobility...
Data storage is an integral part of IT infrastructures, where Quality of Service (QoS) differentiation amongst customers and their applications is essential for many. Achieving this objective in a production environment is nontrivial, because these environments are complex and dynamic. Numerous practical and engineering constraints render the task even more challenging. This paper presents SLED-2,...
This paper considers the problem of how to improve the performance of hybrid storage system employing solid state disks and hard disk drives. We utilize both initial block allocation as well as migration to reach “Wardrop equilibrium”, in which the response times of different devices equalize. We show that such a policy allows adaptive load balancing across devices of different performance. We also...
With the ability to move virtual machines between physical hosts, live migration is a core feature of virtualisation. However for migration to be useful, deployable feature on a large (datacentre) scale, we need to predict migration times with accuracy. In this paper, we characterise the parameters affecting live migration with particular emphasis on the Xen virtualisation platform. We discuss the...
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