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Prospero Media Storage. IGT – . Event. Managing 100TB of small files…. July 2011. Numbers. 70TB used space 700 million files 200GB and 250,000 files uploaded every day 1200Mbps bandwidth throughput in peak 180TB of data is being served out monthly
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Prospero Media Storage IGT – Event Managing 100TB of small files… July 2011
Numbers • 70TBused space • 700 million files • 200GBand 250,000 files uploaded every day • 1200Mbpsbandwidth throughput in peak • 180TBof data is being served out monthly • 3700 Hits per second in peak • 40 storage node servers – 300TB raw space • $0.13 per GB
Motivation • Web 2.0 content serving paradigm shift • Too many files • 12M users x 1 file = very long tail • Too many connections • 1M users + keepalive = 1M connections • Living with modern content in web 2.0 • 1 file x (thumbnail + iPhone + Mac) = 3 file copies
Traditional Architecture HTTP IO IO IO IO Centralized Storage (NAS, SAN, DAS etc.)
Traditional Architecture HTTP – TOO MANY CONNECTIONS IO IO IO IO Centralized Storage (NAS, SAN, DAS etc.)
Traditional Architecture HTTP IO IO IO IO IO IO IO Centralized Storage (NAS, SAN, DAS etc.)
Traditional Architecture HTTP IO IO IO IO IO IO IO Too much IO
Traditional Architecture HTTP Cache IO IO IO IO IO IO IO Centralized Storage (NAS, SAN, DAS etc.)
“There are only two hard things in Computer Science: cache invalidation and naming things”. -- Tim Bray quoting Phil Karlton
Architecture goals • Symmetric identical server nodes • Simplified management and scaling • Linear scaling out • No functional / role servers • No single point of failure • No performance bottlenecks • Multiple datacenters support • DRP support • Geo load distribution
Meet Prospero • Distributed Web content storage system • Full blown HTTP support • Runs on low cost commodity hardware • Adjustable file level replication controls redundancy policy for every content type • Provides dynamic image manipulation
Designed to fail • Fallback for every operation • Geographical, machine, storage medium • Write never fails • All files will reach their destination • Journaling • Tracking all uploaded files • Pending jobs • Guaranteed file distribution
How do we achieve this • Control the input • define the only unified API • Functional process isolation • every function deserves its own process by default • watchdogs • monitors • alerts
get 37D815B5.jpg Go to 37 range servers Fallback if not found 2.static 6.static 0.static 4.static HTTP HTTP HTTP 20-3f 60-7f 00-1f 40-5f 1.static 3.static 7.static 5.static HTTP HTTP HTTP
It’s all about performance • Non blocking IO, readiness notification (epoll) • Asynchronous file IO (AIO) • Zero copy (sendfile) • Memory maps • Inter-process binary protocols • UNIX socket • Minimize dynamic memory allocation • lighttpd memory footprint: 50MB
Lessons learnt • Be symmetric • Control the input • Design to failure • Performance matters again • Simple is hard but a must