Techniques and systems are described for enabling local independent failure domains in a host server or datacenter environment. Included is a locally-attached independent failure device (LA-IFD) with an independent data buffer and a local communications bus for attaching to a host server. Techniques for a communications protocol between the LA-IFD and its host server are provided, including: receiving a request to write a data segment to persistent storage; synchronously storing the data segment in a buffered data segment at the LA-IFD and initiating an asynchronous update of the data segment at a remote storage system; sending a write acknowledgement indicating completion to the requestor; and, after receiving a completion notification from the remote storage system, removing the buffered data segment from the LA-IFD. In some cases, techniques allow a host server and LA-IFD pair to monitor one another for failures and implement a modified protocol in the event of unavailability.