1,527 research outputs found
Understanding and Leveraging Virtualization Technology in Commodity Computing Systems
Commodity computing platforms are imperfect, requiring various enhancements for performance and security purposes. In the past decade, virtualization technology has emerged as a promising trend for commodity computing platforms, ushering many opportunities to optimize the allocation of hardware resources. However, many abstractions offered by virtualization not only make enhancements more challenging, but also complicate the proper understanding of virtualized systems. The current understanding and analysis of these abstractions are far from being satisfactory. This dissertation aims to tackle this problem from a holistic view, by systematically studying the system behaviors. The focus of our work lies in performance implication and security vulnerabilities of a virtualized system.;We start with the first abstraction---an intensive memory multiplexing for I/O of Virtual Machines (VMs)---and present a new technique, called Batmem, to effectively reduce the memory multiplexing overhead of VMs and emulated devices by optimizing the operations of the conventional emulated Memory Mapped I/O in hypervisors. Then we analyze another particular abstraction---a nested file system---and attempt to both quantify and understand the crucial aspects of performance in a variety of settings. Our investigation demonstrates that the choice of a file system at both the guest and hypervisor levels has significant impact upon I/O performance.;Finally, leveraging utilities to manage VM disk images, we present a new patch management framework, called Shadow Patching, to achieve effective software updates. This framework allows system administrators to still take the offline patching approach but retain most of the benefits of live patching by using commonly available virtualization techniques. to demonstrate the effectiveness of the approach, we conduct a series of experiments applying a wide variety of software patches. Our results show that our framework incurs only small overhead in running systems, but can significantly reduce maintenance window
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What are the factors associated with sanitation and hygiene behaviours, an investigation in Giong Trom district, Ben Tre province in the Mekong river Delta region of Vietnam?
Poor sanitation and hygiene are still one of the pressing challenges in the developing world with not only serious health and but also non-health consequences. Diarrheal diseases, for example, are preventable by handwashing and hygienic latrine, still kill more than 4500 children every day, more than that of measles, malaria and HIV combined. Its non-health consequences include welfare loss, dignity, economic and financial losses...Vietnam had a rural sanitation coverage of only 65% despite the great amount of investment (mainly in hardware provision) in rural sanitation and hygiene over the last 25 years. Behaviour change interventions, therefore, are necessary if the country is to achieve Universal Sanitation and good hygiene by 2030 as it committed. Consequently, an understanding of the population’s sanitation and hygiene behavioural determinants is required in order to design efficient and effective intervention programs. This thesis is based on the RANAS model using data surveyed in Giong Trom district, Ben Tre Province (of the provinces with lowest rural sanitation coverage in Vietnam). It has 3 objectives: to identify behavioural determinants and factors associated to a range of sanitation and hygiene behaviours; to identify, measure and compare to health and non-health impact associated with different sanitation conditions; to propose and recommend evidence-backed interventions aimed at improving rural sanitation and hygiene.
Having employed the logistic and multiple linear regression analysis, the thesis found the key factors associated with the following sanitation and hygiene behaviours:
• Hygienic latrine ownership: Source of income, poverty certificate possession, instrumental beliefs, perceived cost.
• Unhygienic latrine ownership (while already having hygienic latrine ownership): Location, disgust, user preference, personal norm.
• Hygienic latrine regular use: Gender, vulnerability perception, Instrumental beliefs, user preference, descriptive norm.
• Handwashing with soap: Knowledge, user preference, disgust, volitional self-efficacy.
• Forgetting handwashing with soap: Gender, knowledge, user preference, disgust, descriptive norm, injunctive norm, volitional self-efficacy, motivational self-efficacy.
In addition, the thesis didn't find clear cut evidence on the health impact of different sanitation conditions due to the fact that it isn't possible to attribute any diseases solely to poor sanitation. However, it found strong evidence that poor sanitation conditions had significant negative welfare impact on the households.
Finally, it demonstrated how a recent intervention program -the WASOBA project- was successful in Ben Tre in increasing hygienic latrine ownership because it addressed directly the key determinant factors identified by this thesis
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