1. A method, comprising: at a computing device comprising one or more processors and storage media storing one or more computer programs executed by the one or more processors to perform the method, performing operations comprising: receiving, from a server, a server journal entry, the server journal entry identifying a plurality of content item blocks of a content item represented by the server journal entry; storing a replication task log entry corresponding to the server journal entry in a replication task log, the replication task log entry identifying the plurality of content item blocks of the content item represented by the server journal entry and identifying an on-premises block server; offering to send the plurality of content item blocks identified in the replication task log entry to the on-premises block server identified in the replication task log entry; receiving, from the on-premises block server, an acceptance of the offer to send the plurality of content item blocks, the acceptance identifying less than all of the plurality of content item blocks; sending less than all of the plurality of content item blocks to the on-premises block server; and updating metadata of the replication task log entry to indicate replication task completion after successfully sending less than all of the plurality of content item blocks to the on-premises block server.