Abstract: A disk mirror data storage system which includes a plurality of mirror facets, at least one local and at least one remote accessed by an IP network. The system includes a mirror volume manager which, in response to a request to store data, performs a synchronous write of the data to the local mirror facet, and an asynchronous write of data to the remote mirror facet. The data to be stored is also written to a locally maintained buffer where it is kept until the asynchronous write to the remote facet has completed. This allows the system to report completion of the write operation after synchronous write to the local facet, and without waiting for the asynchronous write to the remote facet to complete.