Patent ID: 7472173
Filing Date: 2008-12-30
Classification: G06F

Abstract:
1. A remote copying method between a first site and a second site, said first site comprising a first storage system coupled to a first computer and a second storage system coupled to a second computer, and said second site comprising a third storage system and a fourth storage system, said method comprising the following steps: said first storage system adds first order assurance information to first write data received from said first computer, and sends said first write data with said first order assurance information to said third storage system; said second storage system receives second write data from said second computer; said second storage system obtains second order assurance information from said first storage system, adds said second order assurance information to said second write data received from said second computer, and sends said second write data with said second order assurance information to said third storage system; said third storage system writes into a storage area said first write data received from said first storage system and said second write data received from said second storage system in an order based on the first and second order assurance information given to said first and second write data, respectively; and said second storage system holds said first write data received from said first storage system; in the case where a failure occurs in said first storage system, said second storage system sends the first and second write data with the respective first and second order assurance information to said third storage system, said third storage system transfers the first and second write data with the respective first and second order assurance information received from said second storage system to said fourth storage system, and said third storage system and said fourth storage system write into respective storage areas held by said third storage system and said fourth storage system the first and second write data according to the write order based on the first and second order assurance information.