When integrated with push notifications, a live migration function can be used to ensure that systems have a high reliability in cases of hardware failures. However, the dependencies for a large range of hardware devices need to be addressed before realizing emergency live migration. Our platform introduces container-based light virtualization and an automated build function to isolate an application so that it can be deployed on different devices such as Edison, Raspberry Pi model B, BeagleBone Black, and Odroid XU3.

Application loading times can be reduced by prefetching disk blocks into the buffer cache. Existing prefetching schemes for general workloads suffer from significant overheads and low accuracy. ClusterFetch is a lightweight prefetcher that identifies continuous sequences of I/O requests and identifies the files that trigger them. The next time that the same files are opened, the corresponding disk blocks are prefetched. In experiments, ClusterFetch reduced the launch time, by which we refer to the latency that first occurs when a program runs, by 15.2 to 30.9%, and loading times, meaning the delays that are incurred while additional data is loaded from the disk during program execution, by 15.9%.

Application launch time is an important performance metric to user experience in desktop environment. The launch time mostly depends on the performance of secondary storage. There is a cost-performance trade-off in using hard disk drive (HDD) or solid-state drive (SSD). Thus, application launch times can be reduced by utilizing SSDs as caches for slow HDDs. We propose a new SSD caching scheme which migrates data blocks from HDDs to SSDs. Since our scheme operates entirely in the file system level and does not require an extra layer for mapping SSD-cached data, which is essential in most other schemes, our scheme does not incur mapping overheads that cause significant burdens on main memory, CPU, and SSD cache itself. Experimental results demonstrate our scheme yields 56% of performance gain in application launch.

Hard disks are one of the largest sources of power consumption in large-scale storage systems. The disk spin up/down technique has been shown to be an effective solution to this problem. Accordingly, the Open Compute Project (OCP) proposed a storage server for cold data, known as Cold Storage, to reduce power consumption using the spin-down technique in large-scale storage systems. With the aim of making effective use of Cold Storage, we characterize the power consumed by a hard disk in its various modes of operation. We then analyze the workload of an instant messaging service. These our contributions should provide guidelines for the implementation of a stable and energy-efficient distributed file system on a Cold Storage server, and to establish a spin-down policy that is power-proportional and promotes reliability.

New features are often added incrementally to avionics systems to minimize the need for redesign and recertification. However, it then becomes necessary to check that the timing constraints of existing as well as new applications are met. We facilitate these checks by introducing a new data switch that bounds the latency of end-to-end communications across a network. This switch runs a clock-driven switching algorithm that is throughput-optimal with a bounded worst-case delay for all feasible traffic. We propose associated heuristics that determine whether the timing constraints of an integrated modular avionics (IMA) system network that uses this switch are met, even if new features have caused traffic to increase, and then search for alternative network configurations if necessary. Virtual integration is used to make a combined analysis of the worst-case delay in the network and the local buses of individual computing modules. This analysis considers the shared network topology, local hardware architectures, and specified IMA configurations. Our approach can be used by a system architect as an effective method for quickly determining which possible system architectures should be pursued to meet timing constraints, and it allows the cascading effects of changes to be tracked and managed. We demonstrate how these heuristics work through an example in which changes are made to an environmental monitoring facility within an avionics system that uses our switch.

Quality of service (QoS), and in particular reliability and low latency, are essential qualities of safety-critical wireless systems for medical applications. However, wireless links are typically prone to bursts of errors, with characteristics which vary over time. We propose a wireless system suitable for real-time remote patient monitoring in which both the necessary reliability and a bounded end-to-end delay are achieved by an efficient error control scheme. We have paired an example electrocardiography (ECG) application to this wireless system. We also developed a tool chain to assess various combinations of system parameters: we can determine the QoS in terms of the packet-delivery ratio and the end-to-end latency, and also the size of jitter buffer required for seamless ECG monitoring services. A realistic assessment, based on data from the MIT-BIT arrhythmia database, shows that the proposed wireless system can achieve an appropriate level of QoS for real-time ECG monitoring if link-level error control is appropriately implemented.

Reliability is an essential quality of safety-critical wireless systems for medical applications. However, wireless links are typically prone to bursts of errors, with characteristics which vary over time. We propose a wireless system suitable for realtime remote patient monitoring in which the necessary reliability is achieved by an efficient error control in the link layer. We have paired an example electrocardiography application to this wireless system. We also developed a tool chain to determine the reliability, in terms of the packet-delivery ratio, for various combinations of system parameters. A realistic case study, based on data from the MIT-BIT arrhythmia database, shows that the proposed wireless system can achieve an appropriate level of reliability for electrocardiogram monitoring if link-level error control is correctly implemented.