A method and apparatus for mirroring data stored in a storage device within a mass storage system by copying data stored in a first storage device to a second storage device, while simultaneously flushing the write cache. After the two storage devices are synchronized, the applications running on the server that is coupled to the storage devices are temporarily halted to insure that the data is coherent. To obtain coherency, residual data in the write cache may have to be written to both the first and second storage devices. Thereafter, the mirror is broken and the first storage device can begin to be used to store data and the second storage device can be used for other purposes such as facilitating a backup of the data. In this embodiment, since most, if not all, of the data in the write cache is flushed during the time that the first storage device is copied, execution of the applications is only halted for a very short time period.