1. 1 Hussam Abu-Libdeh, Lonnie Princehouse Hakim Weatherspoon Cornell University

2.  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)

5.  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

6.  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)

8.  Consider each cloud provider as a disk in RAID.

9.  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.

11.  Error Coding Recovery

15.  Upload Snapshot

16.  Vendor Migration

17.  Restore snapshot

19.  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.

20. [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.