6,689 research outputs found
The BaBar Event Building and Level-3 Trigger Farm Upgrade
The BaBar experiment is the particle detector at the PEP-II B-factory
facility at the Stanford Linear Accelerator Center. During the summer shutdown
2002 the BaBar Event Building and Level-3 trigger farm were upgraded from 60
Sun Ultra-5 machines and 100MBit/s Ethernet to 50 Dual-CPU 1.4GHz Pentium-III
systems with Gigabit Ethernet. Combined with an upgrade to Gigabit Ethernet on
the source side and a major feature extraction software speedup, this pushes
the performance of the BaBar event builder and L3 filter to 5.5kHz at current
background levels, almost three times the original design rate of 2kHz. For our
specific application the new farm provides 8.5 times the CPU power of the old
system.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, 1 eps figure, PSN MOGT00
Interfacing a high performance disk array file server to a Gigabit LAN
Our previous prototype, RAID-1, identified several bottlenecks in typical file server architectures. The most important bottleneck was the lack of a high-bandwidth path between disk, memory, and the network. Workstation servers, such as the Sun-4/280, have very slow access to peripherals on busses far from the CPU. For the RAID-2 system, we addressed this problem by designing a crossbar interconnect, Xbus board, that provides a 40MB/s path between disk, memory, and the network interfaces. However, this interconnect does not provide the system CPU with low latency access to control the various interfaces. To provide a high data rate to clients on the network, we were forced to carefully and efficiently design the network software. A block diagram of the system hardware architecture is given. In the following subsections, we describe pieces of the RAID-2 file server hardware that had a significant impact on the design of the network interface
Packet reordering, high speed networks and transport protocol performance
We performed end-to-end measurements of UDP/IP flows across an Internet backbone network. Using this data, we characterized the packet reordering processes seen in the network. Our results demonstrate the high prevalence of packet reordering relative to packet loss, and show a strong correlation between packet rate and reordering on the network we studied. We conclude that, given the increased parallelism in modern networks and the demands of high performance applications, new application and protocol designs should treat packet reordering on an equal footing to packet loss, and must be robust and resilient to both in order to achieve high performance
The CMS Event Builder
The data acquisition system of the CMS experiment at the Large Hadron
Collider will employ an event builder which will combine data from about 500
data sources into full events at an aggregate throughput of 100 GByte/s.
Several architectures and switch technologies have been evaluated for the DAQ
Technical Design Report by measurements with test benches and by simulation.
This paper describes studies of an EVB test-bench based on 64 PCs acting as
data sources and data consumers and employing both Gigabit Ethernet and Myrinet
technologies as the interconnect. In the case of Ethernet, protocols based on
Layer-2 frames and on TCP/IP are evaluated. Results from ongoing studies,
including measurements on throughput and scaling are presented.
The architecture of the baseline CMS event builder will be outlined. The
event builder is organised into two stages with intelligent buffers in between.
The first stage contains 64 switches performing a first level of data
concentration by building super-fragments from fragments of 8 data sources. The
second stage combines the 64 super-fragments into full events. This
architecture allows installation of the second stage of the event builder in
steps, with the overall throughput scaling linearly with the number of switches
in the second stage. Possible implementations of the components of the event
builder are discussed and the expected performance of the full event builder is
outlined.Comment: Conference CHEP0
Canadian Hydrogen Intensity Mapping Experiment (CHIME) Pathfinder
A pathfinder version of CHIME (the Canadian Hydrogen Intensity Mapping
Experiment) is currently being commissioned at the Dominion Radio Astrophysical
Observatory (DRAO) in Penticton, BC. The instrument is a hybrid cylindrical
interferometer designed to measure the large scale neutral hydrogen power
spectrum across the redshift range 0.8 to 2.5. The power spectrum will be used
to measure the baryon acoustic oscillation (BAO) scale across this poorly
probed redshift range where dark energy becomes a significant contributor to
the evolution of the Universe. The instrument revives the cylinder design in
radio astronomy with a wide field survey as a primary goal. Modern low-noise
amplifiers and digital processing remove the necessity for the analog
beamforming that characterized previous designs. The Pathfinder consists of two
cylinders 37\,m long by 20\,m wide oriented north-south for a total collecting
area of 1,500 square meters. The cylinders are stationary with no moving parts,
and form a transit instrument with an instantaneous field of view of
100\,degrees by 1-2\,degrees. Each CHIME Pathfinder cylinder has a
feedline with 64 dual polarization feeds placed every 30\,cm which
Nyquist sample the north-south sky over much of the frequency band. The signals
from each dual-polarization feed are independently amplified, filtered to
400-800\,MHz, and directly sampled at 800\,MSps using 8 bits. The correlator is
an FX design, where the Fourier transform channelization is performed in FPGAs,
which are interfaced to a set of GPUs that compute the correlation matrix. The
CHIME Pathfinder is a 1/10th scale prototype version of CHIME and is designed
to detect the BAO feature and constrain the distance-redshift relation.Comment: 20 pages, 12 figures. submitted to Proc. SPIE, Astronomical
Telescopes + Instrumentation (2014
GRAPE-6: The massively-parallel special-purpose computer for astrophysical particle simulation
In this paper, we describe the architecture and performance of the GRAPE-6
system, a massively-parallel special-purpose computer for astrophysical
-body simulations. GRAPE-6 is the successor of GRAPE-4, which was completed
in 1995 and achieved the theoretical peak speed of 1.08 Tflops. As was the case
with GRAPE-4, the primary application of GRAPE-6 is simulation of collisional
systems, though it can be used for collisionless systems. The main differences
between GRAPE-4 and GRAPE-6 are (a) The processor chip of GRAPE-6 integrates 6
force-calculation pipelines, compared to one pipeline of GRAPE-4 (which needed
3 clock cycles to calculate one interaction), (b) the clock speed is increased
from 32 to 90 MHz, and (c) the total number of processor chips is increased
from 1728 to 2048. These improvements resulted in the peak speed of 64 Tflops.
We also discuss the design of the successor of GRAPE-6.Comment: Accepted for publication in PASJ, scheduled to appear in Vol. 55, No.
The role of HiPPI switches in mass storage systems: A five year prospective
New standards are evolving which provide the foundation for multi-gigabit per second data communication structures. The lowest layer protocols are so generalized that they encourage a wide range of application. Specifically, the ANSI High Performance Parallel Interface (HiPPI) is being applied to computer peripheral attachment as well as general data communication networks. The HiPPI Standards suite and technology products which incorporate the standards are introduced. The use of simple HiPPI crosspoint switches to build potentially complex extended 'fabrics' is discussed in detail. Several near term applications of the HiPPI technology are briefly described with additional attention to storage systems. Finally, some related standards are mentioned which may further expand the concepts above
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