A method for copying data to multiple remote sites includes transmitting
data from a first volume in a primary storage system to a back-up volume
provided in a secondary storage system. The primary storage system is
located at a primary site, and the secondary storage system is located at
a first remote site from the primary site. The data from the first volume
in the primary storage system is copied to a second volume in the primary
storage system using a point in time (PiT) as a reference point of time
for the copying. The second volume is provided with a first time
consistent image of the first volume with respect to the reference point
of time. The data from the second volume in the primary storage system is
transferred to a third volume in a ternary storage system at a second
remote site. The third volume is provided with a second time consistent
image of the second volume with respect to the reference point of time,
where the second time consistent image is a mirror image of the first
time consistent image. The data from the third volume is transferred to a
fourth volume in the ternary storage system. The fourth volume is
provided with a third time consistent image. In the ternary storage,
either of the third volume or fourth volume can always keep time
consistent image of the first volume.