Remote Copy Synchronization in Disaster Recovery Computer Systems

A machine-readable medium having computer program product for performing disaster recovery, said computer machine-readable medium comprising:

• computer program code for establishing a remote copy pair relationship between a first storage element and a second storage element by designating said first storage element as a primary disk and said second storage element as a secondary disk, wherein said first storage element handles write requests from a host, and data from said write requests are subsequently copied to said second storage element;
• computer program code for, in response to a loss of connection from said host to said first storage element, designating said secondary storage disk as said primary disk, wherein said second storage element handles write requests from said host;
• computer program code for, in response to a reestablishment of said remote copy pair relationship between said first storage element and said second storage element,
• designating said first storage element as said primary disk and said second storage element as said secondary disk;
• merging a recording bitmap of said second storage element with a recording bitmap of said first storage element;
• and
• copying data that are marked as changed in said merged recording bitmap from said second storage element to said first storage element.