Provided are a method, system, and program for transferring data between system and storage in a shared buffer. An application requests a buffer from a component. The component allocates a buffer and returns to the application a first offset in the buffer for application data and a second offset in the buffer for a first header. The application writes the application data at the first offset in the buffer; and writes the first header at the second offset in the buffer. A second header is written to a third offset in the buffer.