1721718
Recovering internet symmetry in distributed computing
This paper describes two systems to recover the Internet connectivity impaired by private networks and firewalls. These devices cause asymmetry in the Internet, making peer-to-peer computing difficult or even impossible. The Condor system is one of those that are severely impaired by the asymmetry. Compared to normal peer-to-peer computing applications, Condor has stricter requirements, which are representative to any grid computing. To make Condor seamlessly work across private networks and over firewalls, we designed and implemented Dynamic Port Forwarding (DPF) and Generic Connection Brokering (GCB). Both DPF and GCB satisfy the representative requirements. Furthermore DPF supports dedicated large clusters very well because it is simple, efficient, and highly scalable. On the other hand, GCB perfectly supports non-dedicated or personal clusters because it is independent to private network or firewall technologies and does not require airy administrative power to deploy it. In this paper, we describe the implementations of DPF and GCB and analyze them with respect to performance, deployability, security, and scalability.
10201757
Transparent access to Grid resources for user software
Grid computing promises access to large amounts of computing power, but so far adoption of Grid computing has been limited to highly specialized experts for three reasons. First, users are used to batch systems, and interfaces to Grid software are often complex and different to those in batch systems. Second, users are used to having transparent file access, which Grid software does not conveniently provide. Third, efforts to achieve wide-spread coordination of computers while solving the first two problems is hampered when clusters are on private networks. Here we bring together a variety of software that allows users to almost transparently use Grid resources as if they were local resources while providing transparent access to files, even when private networks intervene. As a motivating example, the BaBar Monte Carlo production system is deployed on a truly distributed environment, the European DataGrid, without any modification to the application itself. Copyright © 2005 John Wiley & Sons, Ltd.
9316311
Managing deadline miss ratio and sensor data freshness in real-time databases
The demand for real-time data services is increasing in many applications including e-commerce, agile manufacturing, and telecommunications network management. In these applications, it is desirable to execute transactions within their deadlines, i.e., before the real-world status changes, using fresh (temporally consistent) data. However, meeting these fundamental requirements is challenging due to dynamic workloads and data access patterns in these applications. Further, transaction timeliness and data freshness requirements may conflict. We define average/transient deadline miss ratio and new data freshness metrics to let a database administrator specify the desired quality of real-time data services for a specific application. We also present a novel QoS management architecture for real-time databases to support the desired QoS even in the presence of unpredictable workloads and access patterns. To prevent overload and support the desired QoS, the presented architecture applies feedback control, admission control, and flexible freshness management schemes. A simulation study shows that our QoS-aware approach can achieve a near zero miss ratio and perfect freshness, meeting basic requirements for real-time transaction processing. In contrast, baseline approaches fail to support the desired miss ratio and/or freshness in the presence of unpredictable workloads and data access patterns.
53245873
Using loop invariants to fight soft errors in data caches
30591708
Infrastrukturentscheidungen in vernetzten Unternehmen Eine Wirtschaftlichkeitsanalyse am Beispiel von X.500 Directory Services
To support decisions concerning the planning and implementation of communication infrastructures between six German banking and insurance enterprises, costs and benefits of IT-standards are identified and data are empirically collected, taking X.500-based Directory Services as an example. Potential benefits amount to DM 24 million equivalent to a return on investment of 1100%.
17443081
Software-directed disk power management for scientific applications
Disk power consumption is becoming an increasingly important issue in high-end servers that execute large-scale data-intensive applications. In particular, array-based scientific codes can spend a significant portion of their power budget on the disk subsystem. Observing this, the prior research proposed several strategies, such as spinning down to low-power modes or adjusting the speed of the disk in lower RPM, to reduce power consumption on the disk subsystem. A common characteristic of most of these techniques is that they are reactive, in the sense that they make their decisions based on the disk access patterns observed during execution. While such techniques are certainly useful and the published studies reveal that they can be very effective in some cases, one can conceivably achieve better results by adopting a proactive scheme. Focusing on array-intensive scientific applications, this paper makes two important contributions. First, it presents a compiler-driven proactive approach to disk power management. In this approach, the compiler analyzes the application code and extracts the disk access pattern. It then uses this information to insert explicit disk power management calls in the appropriate places in the code. It also pre-activates a disk (placed into the low-power mode) before it is actually needed to eliminate the potential performance impact of disk power management. The second contribution of this paper is a code transformation approach that can be used to increase the savings coming from a disk power management scheme (whether reactive or proactive). Our experimental results with several scientific application codes show that both the proactive disk power management approach and the disk layout aware code transformations are beneficial from both power consumption and execution time perspectives.
5319461
Energy-aware data prefetching for multi-speed disks
Power consumption of disk based storage systems is becoming an increasingly pressing issue for both commercial and scientific application domains. Prior work proposed several hardware based approaches to reducing disk power consumption by making use of techniques such as spinning down idle disks and rotating them at lower speeds than the maximum speed possible. While such techniques are certainly very important, it is also critical to consider the influence the software can exercise in shaping the power consumption behavior of disk-intensive application programs. Motivated by this, the main goal of this work is to study whether an optimizing compiler can be used for increasing the power benefits that could be obtained from multi-speed disks. Specifically, we propose and experimentally evaluate a compiler-directed energy-aware data prefetching scheme for scientific applications that process disk-resident data sets. This scheme automatically determines the prefetch distance for all disk access instructions, the disk speeds to be employed, and the associated disk layouts (striping parameters) in a unified setting. We implemented the proposed approach within an optimizing compiler framework and conducted experiments with several disk-intensive applications. Our experimental evaluation shows that the proposed approach brings significant reductions in disk energy consumption over a state-of-the-art software-based I/O prefetching mechanism that does not take into account energy consumption explicitly. Our results also show that the energy-aware prefetching scheme does not bring any extra performance penalties and the energy reductions achieved are consistent across a wide spectrum of values of the simulation parameters.