Jaemyoun Lee

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An input/output (I/O) device can incorporate mechanical devices that require physical movements, such as a hard drive seeking a track for a data read or write. Hence I/O operations on a computer can be extremely slow compared to data processing. When a program conducts many I/O operations, the processor often spends most idling as it waits for the I/O(More)
Timing guarantees and predictive early analysis are essential considerations for the design of reliable and verified real-time avionics systems. In this paper, we consider an environmental monitoring avionic system, which allows physical circumstances to be visually monitored continuously in real-time. We analyze timing aspects on the partitions of(More)
New features are often added incrementally to avionics systems to minimize the need for redesign and recertification. However, it thenbecomesnecessary to check that the timing constraints of existing aswell as newapplicationsaremet.We facilitate these checksby introducing anewdata switch that bounds the latencyof end-to-endcommunicationsacrossanetwork. This(More)
Guaranteeing high reliability and acceptable latency are major QoS considerations in the design of life-critical healthcare applications. To achieve those goals over error-prone wireless networks, proper error control is required. We propose a reference system model for wireless telemetry with medical-grade QoS. The system includes the combination of(More)
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(More)
An instant messenger service is one of the most useful mobile apps for exchanging messages and photos with friends. The infrastructural needs of such services are rapidly growing with user demand for high-quality service, and highend computing with sufficient resources are required to meet these demands. However, the amount of power required to maintain(More)
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.(More)
Cloud computing systems require a huge number of storage servers, with growing implications for power bills, carbon emissions and the logistics of data centers. These considerations have motivated researchers to improve the energy efficiency of storage servers. Most servers use a lot of power irrespective of the amount of computing that they are doing, and(More)
The power required to maintain a massive storage infrastructure is impractically high. Although research on the development of energy efficient storage systems has been conducted, it is still insufficient for easily comparing their performances. In this paper, we present a benchmark framework for large-scale object storage servers that is intended at(More)
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(More)