Patent AT-E400021-T1: [Translated] METHOD FOR MAINTAINING COHERENCE BETWEEN MIRROR DATA STORES

The invention provides a storage device controller (200) adapted to be connected to a plurality of storage devices (300) provided with a plurality of storage volumes for storing data, said storage device controller being connectable to an information processing apparatus (100) for sending write requests to the storage volumes, wherein the storage device controller (200) comprises means for forming pairs of storage volumes, each pair bringing one of the plurality of storage volumes into correspondence with another storage volume. The storage device controller (200) is adapted to start to split pairs of a set of paired volumes upon receiving a split command for the set of paired volumes, wherein the storage device controller (200) is adapted to execute a write request being received during splitting the pairs of the set of paired volumes and being addressed to a volume in the set of paired volumes, after a completion of splitting a pair related to the volume in the set of paired volumes.