65,250 research outputs found
A Logical Model and Data Placement Strategies for MEMS Storage Devices
MEMS storage devices are new non-volatile secondary storages that have
outstanding advantages over magnetic disks. MEMS storage devices, however, are
much different from magnetic disks in the structure and access characteristics.
They have thousands of heads called probe tips and provide the following two
major access facilities: (1) flexibility: freely selecting a set of probe tips
for accessing data, (2) parallelism: simultaneously reading and writing data
with the set of probe tips selected. Due to these characteristics, it is
nontrivial to find data placements that fully utilize the capability of MEMS
storage devices. In this paper, we propose a simple logical model called the
Region-Sector (RS) model that abstracts major characteristics affecting data
retrieval performance, such as flexibility and parallelism, from the physical
MEMS storage model. We also suggest heuristic data placement strategies based
on the RS model and derive new data placements for relational data and
two-dimensional spatial data by using those strategies. Experimental results
show that the proposed data placements improve the data retrieval performance
by up to 4.0 times for relational data and by up to 4.8 times for
two-dimensional spatial data of approximately 320 Mbytes compared with those of
existing data placements. Further, these improvements are expected to be more
marked as the database size grows.Comment: 37 page
Elevating commodity storage with the SALSA host translation layer
To satisfy increasing storage demands in both capacity and performance,
industry has turned to multiple storage technologies, including Flash SSDs and
SMR disks. These devices employ a translation layer that conceals the
idiosyncrasies of their mediums and enables random access. Device translation
layers are, however, inherently constrained: resources on the drive are scarce,
they cannot be adapted to application requirements, and lack visibility across
multiple devices. As a result, performance and durability of many storage
devices is severely degraded.
In this paper, we present SALSA: a translation layer that executes on the
host and allows unmodified applications to better utilize commodity storage.
SALSA supports a wide range of single- and multi-device optimizations and,
because is implemented in software, can adapt to specific workloads. We
describe SALSA's design, and demonstrate its significant benefits using
microbenchmarks and case studies based on three applications: MySQL, the Swift
object store, and a video server.Comment: Presented at 2018 IEEE 26th International Symposium on Modeling,
Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS
When Things Matter: A Data-Centric View of the Internet of Things
With the recent advances in radio-frequency identification (RFID), low-cost
wireless sensor devices, and Web technologies, the Internet of Things (IoT)
approach has gained momentum in connecting everyday objects to the Internet and
facilitating machine-to-human and machine-to-machine communication with the
physical world. While IoT offers the capability to connect and integrate both
digital and physical entities, enabling a whole new class of applications and
services, several significant challenges need to be addressed before these
applications and services can be fully realized. A fundamental challenge
centers around managing IoT data, typically produced in dynamic and volatile
environments, which is not only extremely large in scale and volume, but also
noisy, and continuous. This article surveys the main techniques and
state-of-the-art research efforts in IoT from data-centric perspectives,
including data stream processing, data storage models, complex event
processing, and searching in IoT. Open research issues for IoT data management
are also discussed
Extending Message Passing Interface Windows to Storage
This work presents an extension to MPI supporting the one-sided communication
model and window allocations in storage. Our design transparently integrates
with the current MPI implementations, enabling applications to target MPI
windows in storage, memory or both simultaneously, without major modifications.
Initial performance results demonstrate that the presented MPI window extension
could potentially be helpful for a wide-range of use-cases and with
low-overhead
WARP: A ICN architecture for social data
Social network companies maintain complete visibility and ownership of the
data they store. However users should be able to maintain full control over
their content. For this purpose, we propose WARP, an architecture based upon
Information-Centric Networking (ICN) designs, which expands the scope of the
ICN architecture beyond media distribution, to provide data control in social
networks. The benefit of our solution lies in the lightweight nature of the
protocol and in its layered design. With WARP, data distribution and access
policies are enforced on the user side. Data can still be replicated in an ICN
fashion but we introduce control channels, named \textit{thread updates}, which
ensures that the access to the data is always updated to the latest control
policy. WARP decentralizes the social network but still offers APIs so that
social network providers can build products and business models on top of WARP.
Social applications run directly on the user's device and store their data on
the user's \textit{butler} that takes care of encryption and distribution.
Moreover, users can still rely on third parties to have high-availability
without renouncing their privacy
Automated assembly of large space structures using an expert system executive
NASA LaRC has developed a unique testbed for investigating the practical problems associated with the assembly of large space structures using robotic manipulators. The testbed is an interdisciplinary effort which considers the full spectrum of assembly problems from the design of mechanisms to the development of software. This paper will describe the automated structures assembly testbed and its operation, detail the expert system executive and its development, and discuss the planned system evolution. Emphasis will be placed on the expert system development of the program executive. The executive program must be capable of directing and reliably performing complex assembly tasks with the flexibility to recover from realistic system errors. By employing an expert system, information pertaining to the operation of the system was encapsulated concisely within a knowledge base. This lead to a substantial reduction in code, increased flexibility, eased software upgrades, and realized a savings in software maintenance costs
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