32 research outputs found
Degrees of tenant isolation for cloud-hosted software services : a cross-case analysis
A challenge, when implementing multi-tenancy
in a cloud-hosted software service, is how to ensure that the
performance and resource consumption of one tenant does
not adversely affect other tenants. Software designers and
architects must achieve an optimal degree of tenant isolation
for their chosen application requirements. The objective
of this research is to reveal the trade-offs, commonalities,
and differences to be considered when implementing
the required degree of tenant isolation. This research uses
a cross-case analysis of selected open source cloud-hosted
software engineering tools to empirically evaluate varying
degrees of isolation between tenants. Our research reveals
five commonalities across the case studies: disk space reduction,
use of locking, low cloud resource consumption,
customization and use of plug-in architecture, and choice of
multi-tenancy pattern. Two of these common factors compromise
tenant isolation. The degree of isolation is reduced
when there is no strategy to reduce disk space and customization
and plug-in architecture is not adopted. In contrast,
the degree of isolation improves when careful consideration
is given to how to handle a high workload, locking of
data and processes is used to prevent clashes between multiple
tenants and selection of appropriate multi-tenancy pattern. The research also revealed five case study differences:
size of generated data, cloud resource consumption, sensitivity
to workload changes, the effect of the software process,
client latency and bandwidth, and type of software process.
The degree of isolation is impaired, in our results, by
the large size of generated data, high resource consumption
by certain software processes, high or fluctuating workload,
low client latency, and bandwidth when transferring multiple
files between repositories. Additionally, this research
provides a novel explanatory framework for (i) mapping tenant
isolation to different software development processes,
cloud resources and layers of the cloud stack; and (ii) explaining
the different trade-offs to consider affecting tenant
isolation (i.e. resource sharing, the number of users/requests,
customizability, the size of generated data, the scope of control
of the cloud application stack and business constraints)
when implementing multi-tenant cloud-hosted software services.
This research suggests that software architects have
to pay attention to the trade-offs, commonalities, and differences
we identify to achieve their degree of tenant isolation
requirements
Search for Dark Matter with CRESST
The search for direct interactions of dark matter particles remains one of
the most pressing challenges of contemporary experimental physics. A variety of
different approaches is required to probe the available parameter space and to
meet the technological challenges. Here, we review the experimental efforts
towards the detection of direct dark matter interactions using scintillating
crystals at cryogenic temperatures. We outline the ideas behind these detectors
and describe the principles of their operation. Recent developments are
summarized and various results from the search for rare processes are
presented. In the search for direct dark matter interactions, the CRESST-II
experiment delivers competitive limits, with a sensitivity below 5x10^(-7) pb
on the coherent WIMP-nucleon cross section.Comment: Accepted for publication in New Journal of Physics. 25 pages, 18
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The use of social capital in teacher research:A necessary clarification
In this paper, we present a critical reflection on the concept of social capital. We argue that there is no such idea of an umbrella concept of social capital. Instead, two overarching conceptualizations of social capital exist, namely individual social capital and collective social capital. As these conceptualizations of social capital are completely different, we emphasize that studies using social capital as a theoretical lens should clarify the concept as well as be consistent in the interpretation of the concept, from its definition to its methodological operationalization. In this article, we first map the two different conceptualizations of social capital. Next, these conceptualizations are illustrated with well-known teacher research studies, followed by examples of studies in which individual and collective social capital are mixed. Finally, we discuss the consequences of the use and the mix of these different conceptualizations in terms of measurement methods. Additionally, implications for teacher education are presented