Fail-Aware Untrusted Storage

• Published in: 2009 IEEE/IFIP International Conference on Dependable Systems & Networks pp. 494 - 503
• Main Authors: Cachin, C., Keidar, I., Shraer, A.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2009
• Subjects: Cloud computing; Collaborative tools; Collaborative work; Contracts; Laboratories; Online Communities/Technical Collaboration; Protocols; Resists; Stability; Timing
• ISBN: 1424444225; 9781424444229
• ISSN: 1530-0889
• DOI: 10.1109/DSN.2009.5270299

We consider a set of clients collaborating through an online service provider that is subject to attacks, and hence not fully trusted by the clients. We introduce the abstraction of a fail-aware untrusted service, with meaningful semantics even when the provider is faulty. In the common case, when the provider is correct, such a service guarantees consistency (linearizability) and liveness (wait-freedom) of all operations. In addition, the service always provides accurate and complete consistency and failure detection. We illustrate our new abstraction by presenting a Fail-Aware Untrusted STorage service (FAUST). Existing storage protocols in this model guarantee so-called forking semantics. We observe, however, that none of the previously suggested protocols suffice for implementing fail-aware untrusted storage with the desired liveness and consistency properties (at least wait-freedom and linearizability when the server is correct). We present a new storage protocol, which does not suffer from this limitation, and implements a new consistency notion, called weak fork-linearizability. We show how to extend this protocol to provide eventual consistency and failure awareness in FAUST.