Subscribe free to our newsletters via your
. 24/7 Space News .

No-wait data centers
by Staff Writers
Boston MA (SPX) Jul 21, 2014

This simulation of data transfer in a server form demonstrates how Fastpass selects routes through the network so as to avoid congestion at any point between the sender and the receiver. (Enlarge to view animation.) Image courtesy Christine Daniloff and MIT.

Big websites usually maintain their own "data centers," banks of tens or even hundreds of thousands of servers, all passing data back and forth to field users' requests. Like any big, decentralized network, data centers are prone to congestion: Packets of data arriving at the same router at the same time are put in a queue, and if the queues get too long, packets can be delayed.

At the annual conference of the ACM Special Interest Group on Data Communication, in August, MIT researchers will present a new network-management system that, in experiments, reduced the average queue length of routers in a Facebook data center by 99.6 percent - virtually doing away with queues. When network traffic was heavy, the average latency - the delay between the request for an item of information and its arrival - shrank nearly as much, from 3.56 microseconds to 0.23 microseconds.

Like the Internet, most data centers use decentralized communication protocols: Each node in the network decides, based on its own limited observations, how rapidly to send data and which adjacent node to send it to. Decentralized protocols have the advantage of an ability to handle communication over large networks with little administrative oversight.

The MIT system, dubbed Fastpass, instead relies on a central server called an "arbiter" to decide which nodes in the network may send data to which others during which periods of time. "It's not obvious that this is a good idea," says Hari Balakrishnan, the Fujitsu Professor in Electrical Engineering and Computer Science and one of the paper's coauthors.

With Fastpass, a node that wishes to transmit data first issues a request to the arbiter and receives a routing assignment in return. "If you have to pay these maybe 40 microseconds to go to the arbiter, can you really gain much from the whole scheme?" says Jonathan Perry, a graduate student in electrical engineering and computer science (EECS) and another of the paper's authors. "Surprisingly, you can."

Division of labor
Balakrishnan and Perry are joined on the paper by Amy Ousterhout, another graduate student in EECS; Devavrat Shah, the Jamieson Associate Professor of Electrical Engineering and Computer Science; and Hans Fugal of Facebook.

The researchers' experiments indicate that an arbiter with eight cores, or processing units, can keep up with a network transmitting 2.2 terabits of data per second. That's the equivalent of a 2,000-server data center with gigabit-per-second connections transmitting at full bore all the time.

"This paper is not intended to show that you can build this in the world's largest data centers today," Balakrishnan says. "But the question as to whether a more scalable centralized system can be built, we think the answer is yes."

Moreover, "the fact that it's two terabits per second on an eight-core machine is remarkable," Balakrishnan says. "That could have been 200 gigabits per second without the cleverness of the engineering."

The key to Fastpass's efficiency is a technique for splitting up the task of assigning transmission times so that it can be performed in parallel on separate cores. The problem, Balakrishnan says, is one of matching source and destination servers for each time slot.

"If you were asked to parallelize the problem of constructing these matchings," he says, "you would normally try to divide the source-destination pairs into different groups and put this group on one core, this group on another core, and come up with these iterative rounds. This system doesn't do any of that."

Instead, Fastpass assigns each core its own time slot, and the core with the first slot scrolls through the complete list of pending transmission requests. Each time it comes across a pair of servers, neither of which has received an assignment, it schedules them for its slot. All other requests involving either the source or the destination are simply passed on to the next core, which repeats the process with the next time slot. Each core thus receives a slightly attenuated version of the list the previous core analyzed.

Bottom line
Today, to avoid latencies in their networks, most data center operators simply sink more money into them. Fastpass "would reduce the administrative cost and equipment costs and pain and suffering to provide good service to the users," Balakrishnan says. "That allows you to satisfy many more users with the money you would have spent otherwise."

Networks are typically evaluated according to two measures: latency, or the time a single packet of data takes to traverse the network, and throughput, or the total amount of data that can pass through the network in a given interval.


Related Links
Massachusetts Institute of Technology
Space Technology News - Applications and Research

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Speeding up data storage by a thousand times with 'spin current'
Eindhoven, Netherlands (SPX) Jul 11, 2014
A hard drive stores bits in the form of tiny magnetic domains. The directions of the magnetic north and south poles of these domains, which are referred to as the magnetization, determine whether they are a 0 or a 1. Data is stored by changing the direction of the magnetization of the associated bits. At present this is done using a write head to create a local magnetic field, which makes ... read more

Landsat Looks to the Moon

Sky-gazers can expect one 'Supermoon' per month for the next three months

NASA LRO's Moon As Art Collection Is Revealed

Solar photons drive water off the moon

ASU, USGS project yields sharpest map of Mars' surface properties

Curiosity Finds Iron Meteorite on Mars

'Dry Ice' Cause of Gullies on Mars

Further Evidence of Dry Ice Gullies on Mars

NASA Announces Early Career Faculty Space Tech Research Grants

SSERVI: Serving NASA's Mission to the Moon and Beyond, Part 1

Scotland Dominates Locations List For UK Spaceport

Sun Sends More 'Tsunami Waves' to Voyager 1

Chinese moon rover designer shooting for Mars

Yutu designer's bittersweet

Are China's Astronauts Moonbound

Chinese scientists prepare for lunar base life support system

Russian Resupply Spacecraft to Deliver Snails to ISS for Experiments

NASA sends odor-resistant clothes to ISS

Airbus Defence and Space prepares launch of ATV-5 "Georges Lemaitre"

ATV's fiery break-up to be seen from inside

SpaceX Falcon 9 v1.1 Flights Deemed Successful

ISS 'space truck' launch postponed: Arianespace

45th Space Wing launches 6 second-generation ORBCOMM satellites

Sanctions on Russian launchers confers advantage to others

Brown Dwarfs May Wreak Havoc on Orbits of Nearby Planets

Friction from Tides Could Help Distant Earths Survive, and Thrive

Newfound Frozen World Orbits in Binary Star System

Discovery expands search for Earth-like planets

19th Century Math Tactic Tweak Yields Answers 200 Times Faster

A new multi-bit 'spin' for MRAM storage

No-wait data centers

French minister opposes Australian firm's plan to ship waste

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.