A Partial-Distribution-Fault-Aware Protocol for Consistent Updates in Distributed Storage Systems

Distribution of data and erasure tolerant-codes allow to store data reliably in distributed systems. Whereby most techniques are directed to failures of storage resources, also erroneously accessing clients and network interruptions may disturb the storage system operation and cause data loss. Particularly, updates that get partially effective onto distributed data may leave data in an inconsistent state and indirectly destroy data content. Besides, redundancy and data can be left in a state that does not allow to tolerate failures anymore. In this paper, we propose a protocol that takes these issues into account. The protocol forces update consistency in partial distribution scenarios and is correlated with the distribution and coding scheme. It is based on a two-phase commit protocol and a two-layered data structure for buffering updates. For block-wise and sequential access, the protocol cost is hidden in the sequence of accesses related to consecutive blocks.