Experiences Using Web100 Experiences Using Web100 for Visible Human Testbedsfor Visible Human Testbeds

Thomas HackerThomas HackerCenter for Advanced Computing, University of MichiganCenter for Advanced Computing, University of Michigan

Brian AtheyBrian AtheyMichigan Center for Biological Information, University of MichiganMichigan Center for Biological Information, University of Michigan

Web100 Evaluator’s WorkshopWeb100 Evaluator’s WorkshopBoulder, COBoulder, CO

August 1, 2002August 1, 2002

OutlineOutline

Visible Human ProjectVisible Human Project

Edgewarp Visualization ApplicationEdgewarp Visualization Application

Performance ProblemsPerformance Problems

Tuning MethodologyTuning Methodology

ResultsResults

ConclustionConclustion

Visible Human ProjectVisible Human Project

Sponsored by the National Library of Sponsored by the National Library of MedicineMedicineGoal is to deliver rendered images of Goal is to deliver rendered images of anatomic content to teaching stations in anatomic content to teaching stations in the anatomy labthe anatomy labScaling requirements are stringentScaling requirements are stringent At least 40 teaching stations per labAt least 40 teaching stations per lab Simultaneous access by teaching centers Simultaneous access by teaching centers

across the nationacross the nation

EdgewarpEdgewarp

Core component of the Visible Human Core component of the Visible Human Project content deliveryProject content delivery

Designed and developed by Dr. Fred Designed and developed by Dr. Fred Bookstein and Dr. William GreenBookstein and Dr. William Green

Delivers “filmstrip” fly-thorough of Delivers “filmstrip” fly-thorough of anatomical dataanatomical data

Allows students to navigate freely through Allows students to navigate freely through anatomical dataanatomical data

Edgewarp Data AccessEdgewarp Data Access

Edgewarp pulls image voxels from data Edgewarp pulls image voxels from data serverserver

Only the voxels necessary to draw the Only the voxels necessary to draw the current image in detail are pulledcurrent image in detail are pulled

Successively higher resolution voxels are Successively higher resolution voxels are pulled as the image fills inpulled as the image fills in

Allows fast navigation (low-res)Allows fast navigation (low-res)

Provides high resolution still images Provides high resolution still images

Performance ProblemsPerformance Problems

U-M VHP demonstration at NASA AMES U-M VHP demonstration at NASA AMES Gigabit Ethernet Workshop in August, Gigabit Ethernet Workshop in August, 20002000

End-to-end TCP performance from End-to-end TCP performance from University of Michigan to NASA AMES University of Michigan to NASA AMES was around 3 Mb/sec.was around 3 Mb/sec.

Network bottleneck was OC-12!Network bottleneck was OC-12!

No clear cause for performance problemsNo clear cause for performance problems

Web100Web100

Tuning Methodology developed in Tuning Methodology developed in collaboration with PSC staff (Matt Mathis)collaboration with PSC staff (Matt Mathis)

Used Web100 as TCP “oscilloscope” to Used Web100 as TCP “oscilloscope” to guide tuning effortsguide tuning efforts

MethodologyMethodology Start with the wireStart with the wire Work up to TCPWork up to TCP Finish with the applicationFinish with the application

Pre-tuningPre-tuning

Transmission test performed from PSC Transmission test performed from PSC Visible Human Server to University of Visible Human Server to University of MichiganMichigan

Edgewarp test rig used with voxel serverEdgewarp test rig used with voxel server

Initial throughput approximately 12 Mb/secInitial throughput approximately 12 Mb/sec

Network bottleneck was 100 Mb/sec link at Network bottleneck was 100 Mb/sec link at University of MichiganUniversity of Michigan

Pre-tuningPre-tuning

Web100 showed small receiver Web100 showed small receiver socket buffers, little packet loss, socket buffers, little packet loss, poor throughputpoor throughput

Tuning MethodologyTuning Methodology

Start with the wireStart with the wire Used Cat-5e cablingUsed Cat-5e cabling Used good network adaptersUsed good network adapters No congestion losses reported by Network No congestion losses reported by Network

Operations website Operations website Network adaters in full-duplex modeNetwork adaters in full-duplex mode

Tuning MethodologyTuning Methodology

Work up to TCPWork up to TCP Client host tuned to support SACK, MTU Client host tuned to support SACK, MTU

discovery, Timestamps, and Window Scalingdiscovery, Timestamps, and Window Scaling The TCP maximum and default send and The TCP maximum and default send and

receive socket buffer set to 2 MBreceive socket buffer set to 2 MB

The server was checked to ensure that The server was checked to ensure that these options were enabled. these options were enabled.

Web100 Reality CheckWeb100 Reality Check

Check settings in Check settings in Web100 to make sure Web100 to make sure they take effectthey take effect

Check tcpdump to Make Sure…Check tcpdump to Make Sure…# /usr/sbin/tcpdump port 8694Kernel filter, protocol ALL, datagram packet socket tcpdump: listening

on all devices

19:07:26.172433 eth1 > spbuild.engin.umich.edu.1088 > vh.psc.edu.8694: S 1067517561:1067517561(0)

win 32758 <mss 1460,sackOK,timestamp 29833739 0,nop,wscale 5> (DF)

19:07:26.192439 eth1 < vh.psc.edu.8694 > spbuild.engin.umich.edu.1088: S 1021853801:1021853801(0)

ack 1067517562 win 4060 <mss 1460,sackOK,timestamp 1073113995 29833739,nop,wscale 5> (DF)

ResultsResults

Web100 indicated Web100 indicated “sawtooth” “sawtooth” transmission transmission behavior, higher behavior, higher throughput, and throughput, and packet losspacket loss

ResultsResults

Throughput Throughput improved by improved by about a factor of about a factor of fourfour

Effects of Host Tuning on EdgeWarp Data Transmission

Performance

0

20

40

60

UntunedBandw idth

TunedBandw idth

Dat

a Tr

ansm

issi

on

R

ate

(Mb

/sec

)

  n SD 95% CI of Mean Median

Mistuned Bandwidth 

601 1.3121 11.728 to 11.938 12.395

Tuned Bandwidth  601 9.0751 40.613 to 42.067 41.578

ConclusionConclusion

Web100 is an effective tool for diagnosing Web100 is an effective tool for diagnosing TCP performance problemsTCP performance problems

Web100 is an essential aid in tuningWeb100 is an essential aid in tuning

Web100 helps to close the “wizard gap” Web100 helps to close the “wizard gap” necessary to improve performancenecessary to improve performance