adaptive load sharing for clustered digital library servers song, yong-joo system software lab,...
DESCRIPTION
3 Introduction Alexandria digital library Geographically-referenced materials Map, satellite image, digitized aerial photograph Large data Require extensive processing Goal : minimize response timeTRANSCRIPT
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Adaptive Load Sharing for Clustered Digital Library Servers
Song, yong-joo
System Software Lab, EECS, KAIST9. 13, 2000
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Contents Introduction Previous Work
Clustered ADL server design Load sharing strategy Policy for node selection & load collection
Experiment Conclusion & Critique
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3
Introduction Alexandria digital library
Geographically-referenced materials Map, satellite image, digitized aerial photograph
Large data Require extensive processing
Goal : minimize response time
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Introduction(cont’d)
Basic ADL Clustered ADL
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Previous Work Clustered Web server design
DNS round-robin rotation Problem : load imbalance
SWEB Redirecting request by dynamic system load prediction of response time
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SWEB DNS round-robin rotation Redirect request to minimum expected
response time server
CPU, I/O load monitoring
prediction of DB searching time load information update
overhead
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Load Sharing strategy Class of request
Text & image ( CPU & I/O usage small ) DB search ( CPU & I/O usage maybe large ) Image processing ( predictable )
Relative Server-site Response Cost Availability relative to the unloaded base node
redirection threshold value
atioDiskAvailRdthDiskBandwindwidthBaseDiskBa
IdleRatioCPUSpeededBaseCPUSpeRSRC
)1(
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Policy for load collection Broadcast – redundant info, load explosion Random poll – synchronization overhead
Proposed Random multicast
A hybrid approach Random multicast + Random poll
)1)(1()1( atioDiskAvailRIdleRatio
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Experiment Server
6 of 147Mhz 2 of dual 167Mhz
Multi-node performance Comparison of load collection policies Effectiveness of RSRC func.
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Conclusion Study adaptive load balancing strategy
Consider both I/O & CPU load factor On non-uniform cluster Hybrid node selection & collection policy
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Critique SWEB does not consider non-uniform
cluster? RSRC correctness Parameter, threshold value decision Multicast overhead
How about Broadcast & selective catch