RACS: A Case for Cloud Storage Diversity

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Hussam Abu-Libdeh,Lonnie PrincehouseHakim WeatherspoonCornell University

Problem

Vendor Lock-in:Longer time they use one cloud provider more data stored in this cloud provider harder and more expensive to transfer their data out (transfer in $$$$, transfer out $$$$) Lock in one cloud provider More vulnerable for price hikes/data center failures(Two main problems)

Internet Archive--Data Transfer

Internet Archive—Read/Write

Stuck in one cloud provider Outage and operation failure:

physical failure Google Cloud unavailable Microsoft data center failure in Oct. 2009

Economic failures: budget now allowed Emerging new cheaper cloud Current cloud provider increase price

How to guard against Vendor Lock-in First thought:

Why not replicate their data into multiple providers? ▪ Could not; three replicas, too expensive

Another way to create redundancy: ▪ Error Correcting code (such as RAID 5)

Preliminary knowledge: RAID 5

Redundant Array of Cloud Storage Consider each cloud provider as a disk

in RAID.

Design

Implemented as Proxy between client application and n- cloud storages Strip data into m

pieces, put them into m clouds, and generate (n-m) redundant data.

Distributed RACS

Failures Recovery

Error Coding Recovery

Cost of hosting on the cloud

Cost of Switching Vendors

Tolerant a Vendor Price Hike

Different Scenarios (1)

Upload Snapshot

Different Scenarios

Vendor Migration

Different Scenarios (3)

Restore snapshot

RACS performance

Conclusion

Identified an important problem: vendor lock-in

Proposed Redundant Array of Cloud Storage to solve this problem using erasure coding.

Tradeoff between overhead expense and vendor mobility

Simulations and experiments to prove the virtue for RACS.

Reference

[1] RACS: A Case for Cloud Storage Diversity. Hussam Abu-Libdeh, Lonnie Princehouse, Hakim Weatherspoon. ACM Symposium on Cloud Computing (SOCC). June 2010, Indianapolis, IN.