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Unformatted text preview: RACS: A Case for Cloud Storage Diversity Hussam Abu-Libdeh Cornell University Ithaca, NY 14853 [email protected] Lonnie Princehouse Cornell University Ithaca, NY 14853 [email protected] Hakim Weatherspoon Cornell University Ithaca, NY 14853 [email protected] ABSTRACT The increasing popularity of cloud storage is leading organizations to consider moving data out of their own data centers and into the cloud. However, success for cloud storage providers can present a significant risk to customers; namely, it becomes very expensive to switch storage providers. In this paper, we make a case for apply- ing RAID-like techniques used by disks and file systems, but at the cloud storage level. We argue that striping user data across multi- ple providers can allow customers to avoid vendor lock-in, reduce the cost of switching providers, and better tolerate provider outages or failures. We introduce RACS, a proxy that transparently spreads the storage load over many providers. We evaluate a prototype of our system and estimate the costs incurred and benefits reaped. Fi- nally, we use trace-driven simulations to demonstrate how RACS can reduce the cost of switching storage vendors for a large or- ganization such as the Internet Archive by seven-fold or more by varying erasure-coding parameters. Categories and Subject Descriptors C.2.4 [ Computer Systems Organization ]: Computer Commu- nication Networks— Distributed Systems ; D.4.3 [ OPERATING SYSTEMS ]: File Systems Management— Distributed File Sys- tems ; D.4.5 [ OPERATING SYSTEMS ]: Reliability— Fault- tolerance ; D.0 [ SOFTWARE ]: General—Distributed wide-area storage systems General Terms Design, Economics, Reliability Keywords Cloud computing, cloud storage, distributed systems, vendor lock- in, erasure codes, fault tolerance 1. INTRODUCTION Current trends show an increasing number of companies and or- ganizations migrating their data to cloud storage providers . Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. SoCC’10, June 10–11, 2010, Indianapolis, Indiana, USA. Copyright 2010 ACM 978-1-4503-0036-0/10/06 ...$10.00. Typical usage examples include storing online users’ account data, off-site backup storage, and content distribution, to name a few. In fact, one impressive pilot program and motivating example is a recent announcement by the United States Library of Congress to move its digitized content to the cloud . Other participants in that program include the New York Public Library and the Biodi- versity Heritage Library....
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