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The use of flash based Solid State Drives (SSDs) has expanded rapidly into the cloud computing environment. In cloud computing, ensuring the service level objective (SLO) of each server is the major criterion in designing a system. In particular, eliminating performance interference among virtual machines (VMs) on shared storage is a key challenge. However, studies on SSD performance to guarantee SLO in such environments are limited. In this paper, we present analysis of I/O behavior for a shared SSD as storage in terms of proportionality and stability. We show that performance SLOs of SSD based storage systems being shared by VMs or tasks are not satisfactory. We present and analyze the reasons behind the unexpected behavior through examining the components of SSDs such as channels, DRAM buffer, and Native Command Queuing (NCQ). We introduce two novel SSD-aware host level I/O schedulers on Linux, called A & x002B;CFQ and H & x002B;BFQ, based on our analysis and findings. Through experiments on Linux, we analyze I/O proportionality and stability in multi-tenant environments. In addition, through experiments using real workloads, we analyze the performance interference between workloads on a shared SSD. We then show that the proposed I/O schedulers almost eliminate the interference effect seen in CFQ and BFQ, while still providing I/O proportionality and stability for various I/O weighted scenarios. ; National Research Foundation of Korea (NRF) - Korea Government (MSIT) [NRF-2019R1A2C2009476] ; This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIT) under Grant NRF-2019R1A2C2009476.

In recent years, scholars in the fields of refugee studies and forced migration have extended their areas of interest and research into the phenomenon of displacement, human response to it, and ways to intervene to assist those affected, increasingly focusing on the emotional and social impact of displacement on refugees and their adjustment to the traumatic experiences. In the process, the positive concept of "psychosocial wellness" was developed as discussed in this volume. In it noted scholars address the strengths and limitations of their investigations, citing examples from their work with refugees from Afghanistan, Cambodia, Vietnam, Palestine, Cuba, Nicaragua, Haiti, Eastern Europe, Bosnia, and Chile. The authors discuss how they define "psychosocial wellness," as well as the issues of sample selection, measurement, reliability and validity, refugee narratives and "voices," and the ability to generalize findings and apply these to other populations. The key question that has guided many of these investigations and underlies the premise of this book is "what happens to an ordinary person who has experienced an extraordinary event?" This volume also highlights the fact that those involved in such research must also deal with their own emotional responses as they hear victims tell of killing, torture, humiliation, and dispossesion. The volume will therefore appeal to practitioners of psychology, psychiatry, social work, nursing, and anthropology. However, its breadth and the evaluation of the strengths and disadvantages of both qualitative and quantitative methods also make it an excellent text for students