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OceanStore is a global persistent data store designed to scale tobillions of users.It provides a consistent, highly-available, and durablestorage utility atop an infrastructure comprised of untrusted servers.
Any computer can join the infrastructure, contributing storage orproviding local user access in exchange for economic compensation.Users need only subscribe to a single OceanStore service provider,although they may consume storage and bandwidth from many differentproviders. The providers automatically buy and sell capacity and coverage amongthemselves, transparently to the users.The utility model thus combines the resources from federated systemsto provide a quality of service higher than that achievable by anysingle company.
OceanStore caches data promiscuously; any server may create alocal replica of any data object. These local replicas provide fasteraccess and robustness to network partitions. They also reduce networkcongestion by localizing access traffic.
We must assume that any server in the infrastructure maycrash, leak information, or become compromised. Promiscuous cachingtherefore requires redundancy and cryptographic techniques to protectthe data from the servers upon which it resides.
OceanStore employs a Byzantine-fault tolerant commit protocol toprovide strong consistency across replicas. The OceanStore API alsoallows applications to weaken their consistency restrictions inexchange for higher performance and availability.
A version-based archival storage system provides durability whichexceeds today's best by orders of magnitude. OceanStore stores eachversion of a data object in a permanent, read-only form, which isencoded with an erasure code and spread over hundreds or thousands ofservers. A small subset of the encoded fragments are sufficient toreconstruct the archived object; only a global-scale disaster coulddisable enough machines to destroy the archived object.
The OceanStore introspection layer adapts the system to improveperformance and fault tolerance. Internal event monitors collect andanalyze information such as usage patterns, network activity, andresource availability. OceanStore can then adapt to regional outagesand denial of service attacks, pro-actively migrate data towards areasof use and maintain sufficiently high levels of data redundancy.
Many components of OceanStore are already functioning in isolation. Acomplete prototype is currently under development.