Abstract: Data transfer to computing elements is synchronized in a computer system that includes the computing elements and controllers that provide data from data sources to the computing elements. A request for data made by a computing element is intercepted and transmitted to the controllers. At least a first controller responds by transmitting requested data to the computing element and by indicating how a second controller will respond to the intercepted request.

Abstract: Data transfer to computing elements is synchronized in a computer system that includes the computing elements and controllers that provide data from data sources to the computing elements. A request for data made by a computing element is intercepted and transmitted to the controllers. At least a first controller responds by transmitting requested data to the computing element and by indicating how a second controller will respond to the intercepted request.

Abstract: A mirror set copy from a first storage device to a second storage device is performed in a computer system in which write requests are each associated with a reference label. Write requests and a mirror read request are received at the first storage device, and the write requests also are received at the second storage device. The write requests are processed at the first storage device processes. Data is read from the first storage device in response to the mirror read request. The first storage device then sends the data to the second storage device along with a reference label of a write request received at the first storage device prior to sending the data. Thereafter, the second storage device writes the data. Finally, the second storage device processes write requests until the second storage device encounters a write request having the same reference label as that sent with the data.