236 research outputs found
Construction of Partial MDS and Sector-Disk Codes With Two Global Parity Symbols
Partial MDS (PMDS) codes are erasure codes combining local (row) correction with global additional correction of entries, while sector-disk (SD) codes are erasure codes that address the mixed failure mode of current redundant arrays of independent disk (RAID) systems. It has been an open problem to construct general codes that have the PMDS and the SD properties, and previous work has relied on Monte-Carlo searches. In this paper, we present a general construction that addresses the case of any number of failed disks and in addition, two erased sectors. The construction requires a modest field size. This result generalizes previous constructions extending RAID 5 and RAID 6
Functional Specification of the RAVENS Neuroprocessor
RAVENS is a neuroprocessor that has been developed by the TENNLab research
group at the University of Tennessee. Its main focus has been as a vehicle for
chip design with memristive elements; however it has also been the vehicle for
all-digital CMOS development, plus it has implementations on FPGA's,
microcontrollers and software simulation. The software simulation is supported
by the TENNLab neuromorphic software framework so that researchers may develop
RAVENS solutions for a variety of neuromorphic computing applications. This
document provides a functional specification of RAVENS that should apply to all
implementations of the RAVENS neuroprocessor.Comment: 17 pages, 11 figure
Disclosure of a Neuromorphic Starter Kit
This paper presents a Neuromorphic Starter Kit, which has been designed to
help a variety of research groups perform research, exploration and real-world
demonstrations of brain-based, neuromorphic processors and hardware
environments. A prototype kit has been built and tested. We explain the
motivation behind the kit, its design and composition, and a prototype physical
demonstration.Comment: 4 pages, 3 figure
Optimizations for a Current-Controlled Memristor-based Neuromorphic Synapse Design
The synapse is a key element of neuromorphic computing in terms of efficiency
and accuracy. In this paper, an optimized current-controlled memristive synapse
circuit is proposed. Our proposed synapse demonstrates reliability in the face
of process variation and the inherent stochastic behavior of memristors. Up to
an 82% energy optimization can be seen during the SET operation over prior
work. In addition, the READ process shows up to 54% energy savings. Our
current-controlled approach also provides more reliable programming over
traditional programming methods. This design is demonstrated with a 4-bit
memory precision configuration. Using a spiking neural network (SNN), a
neuromorphic application analysis was performed with this precision
configuration. Our optimized design showed up to 82% improvement in control
applications and a 2.7x improvement in classification applications compared
with other design cases
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Hydrographic, chemical and optical observations from legs 4 and 5, YALOC-71
Hydrographic, chemical and optical data collected on legs 4 and 5 (November and December, 1971) of YALOC-71 in the vicinity of the Panama Basin are presented. The measurements were made for two purposes--to study the behavior of the Cromwell Current near the Galapagos Islands and to study the suspended particulate matter in the Panama Basin
Construction of Partial MDS and Sector-Disk Codes With Two Global Parity Symbols
Partial MDS (PMDS) codes are erasure codes combining local (row) correction with global additional correction of entries, while sector-disk (SD) codes are erasure codes that address the mixed failure mode of current redundant arrays of independent disk (RAID) systems. It has been an open problem to construct general codes that have the PMDS and the SD properties, and previous work has relied on Monte-Carlo searches. In this paper, we present a general construction that addresses the case of any number of failed disks and in addition, two erased sectors. The construction requires a modest field size. This result generalizes previous constructions extending RAID 5 and RAID 6
Rethinking Erasure Codes for Cloud File Systems: Minimizing I/O for Recovery and Degraded Reads,”
Abstract To reduce storage overhead, cloud file systems are transitioning from replication to erasure codes. This process has revealed new dimensions on which to evaluate the performance of different coding schemes: the amount of data used in recovery and when performing degraded reads. We present an algorithm that finds the optimal number of codeword symbols needed for recovery for any XOR-based erasure code and produces recovery schedules that use a minimum amount of data. We differentiate popular erasure codes based on this criterion and demonstrate that the differences improve I/O performance in practice for the large block sizes used in cloud file systems. Several cloud systems [Ford10,Calder11] have adopted Reed-Solomon (RS) codes, because of their generality and their ability to tolerate larger numbers of failures. We define a new class of rotated ReedSolomon codes that perform degraded reads more efficiently than all known codes, but otherwise inherit the reliability and performance properties of Reed-Solomon codes. The online home for this paper may be found at: http://web.eecs.utk.edu/~plank/plank/papers/ FAST-2012 Abstract To reduce storage overhead, cloud file systems are transitioning from replication to erasure codes. This process has revealed new dimensions on which to evaluate the performance of different coding schemes: the amount of data used in recovery and when performing degraded reads. We present an algorithm that finds the optimal number of codeword symbols needed for recovery for any XOR-based erasure code and produces recovery schedules that use a minimum amount of data. We differentiate popular erasure codes based on this criterion and demonstrate that the differences improve I/O performance in practice for the large block sizes used in cloud file systems. Several cloud system
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