6,078 research outputs found
HVSTO: Efficient Privacy Preserving Hybrid Storage in Cloud Data Center
In cloud data center, shared storage with good management is a main structure
used for the storage of virtual machines (VM). In this paper, we proposed
Hybrid VM storage (HVSTO), a privacy preserving shared storage system designed
for the virtual machine storage in large-scale cloud data center. Unlike
traditional shared storage, HVSTO adopts a distributed structure to preserve
privacy of virtual machines, which are a threat in traditional centralized
structure. To improve the performance of I/O latency in this distributed
structure, we use a hybrid system to combine solid state disk and distributed
storage. From the evaluation of our demonstration system, HVSTO provides a
scalable and sufficient throughput for the platform as a service
infrastructure.Comment: 7 pages, 8 figures, in proceeding of The Second International
Workshop on Security and Privacy in Big Data (BigSecurity 2014
Dynamic Physiological Partitioning on a Shared-nothing Database Cluster
Traditional DBMS servers are usually over-provisioned for most of their daily
workloads and, because they do not show good-enough energy proportionality,
waste a lot of energy while underutilized. A cluster of small (wimpy) servers,
where its size can be dynamically adjusted to the current workload, offers
better energy characteristics for these workloads. Yet, data migration,
necessary to balance utilization among the nodes, is a non-trivial and
time-consuming task that may consume the energy saved. For this reason, a
sophisticated and easy to adjust partitioning scheme fostering dynamic
reorganization is needed. In this paper, we adapt a technique originally
created for SMP systems, called physiological partitioning, to distribute data
among nodes, that allows to easily repartition data without interrupting
transactions. We dynamically partition DB tables based on the nodes'
utilization and given energy constraints and compare our approach with physical
partitioning and logical partitioning methods. To quantify possible energy
saving and its conceivable drawback on query runtimes, we evaluate our
implementation on an experimental cluster and compare the results w.r.t.
performance and energy consumption. Depending on the workload, we can
substantially save energy without sacrificing too much performance
Development of a software interface for optical disk archival storage for a new life sciences flight experiments computer
The current Life Sciences Laboratory Equipment (LSLE) microcomputer for life sciences experiment data acquisition is now obsolete. Among the weaknesses of the current microcomputer are small memory size, relatively slow analog data sampling rates, and the lack of a bulk data storage device. While life science investigators normally prefer data to be transmitted to Earth as it is taken, this is not always possible. No down-link exists for experiments performed in the Shuttle middeck region. One important aspect of a replacement microcomputer is provision for in-flight storage of experimental data. The Write Once, Read Many (WORM) optical disk was studied because of its high storage density, data integrity, and the availability of a space-qualified unit. In keeping with the goals for a replacement microcomputer based upon commercially available components and standard interfaces, the system studied includes a Small Computer System Interface (SCSI) for interfacing the WORM drive. The system itself is designed around the STD bus, using readily available boards. Configurations examined were: (1) master processor board and slave processor board with the SCSI interface; (2) master processor with SCSI interface; (3) master processor with SCSI and Direct Memory Access (DMA); (4) master processor controlling a separate STD bus SCSI board; and (5) master processor controlling a separate STD bus SCSI board with DMA
Orbital Perturbations of the Galilean Satellites During Planetary Encounters
The Nice model of the dynamical instability and migration of the giant
planets can explain many properties of the present Solar System, and can be
used to constrain its early architecture. In the jumping-Jupiter version of the
Nice model, required from the terrestrial planet constraint and dynamical
structure of the asteroid belt, Jupiter has encounters with an ice giant. Here
we study the survival of the Galilean satellites in the jumping-Jupiter model.
This is an important concern because the ice-giant encounters, if deep enough,
could dynamically perturb the orbits of the Galilean satellites, and lead to
implausible results. We performed numerical integrations where we tracked the
effect of planetary encounters on the Galilean moons. We considered three
instability cases from Nesvorny & Morbidelli (2012) that differed in the number
and distribution of encounters. We found that in one case, where the number of
close encounters was relatively small, the Galilean satellite orbits were not
significantly affected. In the other two, the orbital eccentricities of all
moons were excited by encounters, Callisto's semimajor axis changed, and, in a
large fraction of trials, the Laplace resonance of the inner three moons was
disrupted. The subsequent evolution by tides damps eccentricities and can
recapture the moons in the Laplace resonance. A more important constraint is
represented by the orbital inclinations of the moons, which can be excited
during the encounters and not appreciably damped by tides. We find that one
instability case taken from Nesvorny & Morbidelli (2012) clearly fails this
constraint. This shows how the regular satellites of Jupiter can be used to set
limits on the properties of encounters in the jumping-Jupiter model, and help
us to better understand how the early Solar System evolved.Comment: The Astronomical Journal, in pres
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Joseph Smith’s First Vision: New Methods for the Analysis of Experience-Related Texts
s-Processing in the Galactic Disk. I. Super-Solar Abundances of Y, Zr, La, Ce in Young Open Clusters
In a recent study, based on homogeneous barium abundance measurements in open
clusters, a trend of increasing [Ba/Fe] ratios for decreasing cluster age was
reported. We present here further abundance determinations, relative to four
other elements hav- ing important s-process contributions, with the aim of
investigating whether the growth found for [Ba/Fe] is or not indicative of a
general property, shared also by the other heavy elements formed by slow
neutron captures. In particular, we derived abundances for yttrium, zirconium,
lanthanum and cerium, using equivalent widths measurements and the MOOG code.
Our sample includes 19 open clusters of different ages, for which the spectra
were obtained at the ESO VLT telescope, using the UVES spectrometer. The growth
previously suggested for Ba is confirmed for all the elements analyzed in our
study. This fact implies significant changes in our views of the Galactic
chemical evolution for elements beyond iron. Our results necessarily require
that very low-mass AGB stars (M < 1.5M\odot) produce larger amounts of
s-process elements (hence acti- vate the 13 C-neutron source more effectively)
than previously expected. Their role in producing neutron-rich elements in the
Galactic disk has been so far underestimated and their evolution and
neutron-capture nucleosynthesis should now be reconsidered.Comment: ApJ accepte
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