Causally consistent distributed storage systems have received significant recent attention due to the potential for providing a low latency data access as compared with linearizability. Current causally consistent data stores use partial or full replication to ensure data access to clients over a distributed setting. In this paper, we develop, for the first time, an erasure coding based algorithm called CausalEC that ensures causal consistency for a collection of read-write objects stored in a distributed set of nodes over an asynchronous message passing system. CausalEC can use an arbitrary linear erasure code for data storage, and ensures liveness and storage properties prescribed by the erasure code. CausalEC retains a key benefit of previously designed replication-based algorithms - every write operation is local, that is, a server performs only local actions before returning to a client that issued a write operation. For servers that store certain objects in an uncoded manner, read operations to those objects also return locally. In general, a read operation to an object can be returned by a server on contacting a small subset of other servers so long as the underlying erasure code allows for the object to be decoded from that subset. As a byproduct, we develop EventualEC, a new eventually consistent erasure coding based data storage algorithm. A novel technical aspect of CausalEC is the use of cross-object erasure coding, where nodes encode values across multiple objects, unlike previous consistent erasure coding based solutions. CausalEC navigates the technical challenges of cross-object erasure coding, in particular, pertaining to re-encoding the objects when writes update the values and ensuring that reads are served in the transient state where the system transitions to storing the codeword symbols corresponding to the new object versions.

中文翻译：

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CausalEC：基于跨对象擦除编码的因果一致数据存储算法

与线性化相比，因果一致的分布式存储系统由于具有提供低延迟数据访问的潜力而受到了近期的广泛关注。当前因果一致的数据存储使用部分​​或完全复制来确保通过分布式设置对客户端的数据访问。在本文中，我们首次开发了一种基于纠删码的算法，称为CausalEC，该算法可确保异步消息传递系统上存储在一组分布式节点中的读写对象集合的因果一致性。CausalEC可以使用任意线性擦除代码进行数据存储，并确保擦除代码规定的活动性和存储属性。CausalEC保留了以前设计的基于复制的算法的主要优点-每个写操作都是本地的，也就是说，服务器仅返回返回发出写操作的客户端之前的本地操作。对于以未编码方式存储某些对象的服务器，对这些对象的读取操作也会在本地返回。通常，只要底层擦除代码允许从该子集中解码对象，服务器就可以在与其他服务器的一小部分子集联系时返回对对象的读取操作。作为副产品，我们开发了EventualEC，这是一种新的最终一致的基于擦除编码的数据存储算法。CausalEC的一个新颖的技术方面是跨对象擦除编码的使用，与以前基于一致擦除编码的解决方案不同，其中节点跨多个对象编码值。CausalEC应对跨对象擦除编码的技术挑战，特别是，