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Slingshot: Deploying Stateful Services in Wireless Hotspots

This paper discusses Slingshot, a system for deploying stateful services in wireless hotspots, addressing limitations in resources, performance, bandwidth, and latency. It introduces the concept of replicas and leverages portable storage to ensure availability and minimize state loss. The system is evaluated and compared to remote execution, demonstrating its effectiveness in speeding up service instantiation. Related work and conclusions are also presented.

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Slingshot: Deploying Stateful Services in Wireless Hotspots

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  1. Slingshot: Deploying Stateful Services in Wireless Hotspots Ya-Yunn Su Jason Flinn University of Michigan

  2. Performance Portability Motivation Mobile Computer • Portable: take everywhere • Easy to carry and less obtrusive • Limited in resources • Performance: run demanding applications • More processing power and storage capacity • Bulkier and heavier

  3. Limited bandwidth High latency Remote Execution Internet Wireless Hotspot VNC Server AP VNC client

  4. VM VNC Home Server Surrogate Cyber Foraging Internet Wireless Hotspot AP VNC client

  5. VM VNC Home Server Surrogate Migrating Remote Services Internet Wireless Hotspot AP • Problems: • No service during migration VNC client • Loss state on surrogate failure

  6. VM VNC VM VNC Home Server Slingshot: Replicate Services Internet Wireless Hotspot AP Surrogate VNC client • Home replica always available • No state loss on surrogate failure

  7. Ease of Management • Surrogates should be appliances • Slingshot • Minimizes the surrogate computing base • Uses a heavyweight virtual machine • Places no hard state on surrogates

  8. Outline • Motivation • Implementation • Evaluation • Related Work • Conclusion

  9. VM VNC Slingshot Overview VM VNC VM VNC Surrogate Surrogate Home Server Request Request Request VNC proxy • Slingshot applications • - Remote desktop: VNC • - Speech recognition: IBM ViaVoice VNC client

  10. State of a Remote Service • The virtual machine state contains: Volatile state: memory image and registers • Unique to each service • Compressed and stored as individual files Persistent state: virtual disk image • Large: ex. 4 GB for our VNC service • Stored in content addressable database

  11. Content Addressable Database Disk Blocks Chunk Table for VNC Hash Table Chunk Database • This runs on the home server • Built upon Internet Suspend Resume • [ Kozuch02] Chunk Table for Speech Recognition

  12. VM2 Speech Surrogate VM1 VNC Content Addressable Database data Home Server data Content Addressable Cache • Persistent state can be • - Fetched on demand • - Shared between applications Surrogate

  13. Creating a Replica • Big idea: recreate current state from • Checkpoint on the home server • Event log on the client • Application level determinism • Example: Checkpoint + Event Log = Current State

  14. VM VNC VM VNC VM VNC SLOW! 3. Replay event log 2. Log requests Instantiate a Replica 1. Checkpoint 2. Transfer volatile state and chunk table Surrogate Home server VNC proxy VNC client

  15. VM VNC VM VNC VM VNC 1. Transfer volatile state, chunk table and hash table 2. Replay event log 1. Log requests Leveraging Portable Storage Surrogate Home server VNC proxy • Portable storage carries: • Volatile state • Content addressable database VNC client

  16. Outline • Motivation • Design Principles • Implementation • Evaluation • Related Work • Conclusion

  17. VM VNC VM VNC Network Topology Internet 30 ms latency 1.5 Mbps 1.5 Mbps 1.5 Mbps 256 Kbps AP Surrogate Home Server • Workload: open Word, insert text, save document and close Word

  18. Benefit of Slingshot • Slingshot: 2.6 times faster than remote execution

  19. VM VNC Network Topology Internet 30 ms latency 1.5 Mbps 1.5 Mbps 1.5 Mbps 256 Kbps AP Surrogate Home Server Handheld

  20. : Remote execution : Slingshot : Slingshot w/ microdrive : Remote execution : Slingshot Instantiating the First Replica • Slingshot executes 2.6 times faster than remote execution

  21. VNC VNC VM VM Network Topology Internet 15 ms latency 15 ms latency 1.5 Mbps 1.5 Mbps 1.5 Mbps 1.5 Mbps 1.5 Mbps 256 Kbps AP AP Nearby Surrogate Distant Surrogate Home Server Handheld device

  22. : Remote execution : Without microdrive : With microdrive : Remote execution : Without microdrive Instantiating Another Replica

  23. Related Work • Cyber foraging [Balan03, Goyal04] • Support user mobility and stateful services • Virtual machine/process migration [Sapuntzakis02, Kozuch02, Tolia03] • Apply the same optimization techniques • Replicate VM to service mobile computers • Replay at different level [Dunlap02, Bressoud95, Rodrigues01, Brown02] • Enforce determinism at the application level

  24. Conclusion • Slingshot • Is 2.6x faster than remote execution • Hides surrogate failure • Minimizes surrogate maintenance cost • Questions?

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