The former case is called a "local/global" conflict, and the latter case a "server/server" conflict. Optimistic replication can potentially cause concurrent updates to different servers on the same object, preventing replication. Disconnected operation's local updates can potentially clash with other connected users' updates on the same objects, preventing reintegration. These unique features introduce the possibility of semantically diverging copies of the same files or directories, known as "conflicts". Coda allows all servers to receive updates, allowing for a greater availability of server data in the event of network partitions, a case which AFS cannot handle. AFS uses a pessimistic replication strategy with its files, only allowing one read/write server to receive updates and all other servers acting as read-only replicas. Then it transitions back to normal connected-mode operation.Īlso different from AFS is Coda's data replication method. Upon network reconnection, the client moves to reintegration state it sends logged updates to the servers. This operating state is called disconnected operation. If the network connection is lost, the Coda client's local cache serves data from this cache and logs all updates. During normal operation, a user reads and writes to the file system normally, while the client fetches, or "hoards", all of the data the user has listed as important in the event of network disconnection.
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