Remote data copying among storage systems

Abstract

The present invention provides a method for guaranteeing a data consistency among a plurality of storages and sites, when data transfer is performed by asynchronous remote copying from a site including a plurality of storages. When writing is made into a first storage system or a second storage system, the storage system that received the writing transfers the write data to the other storage system within the site by synchronous remote copying. At this timing the first storage system gives the write data information for order assurance. Furthermore, the first or the second storage system transfers the write data and thus given information for order assurance to the third or the fourth storage system by asynchronous remote copying. Furthermore, the third or the fourth storage system which has received the write data transfers to the other storage system within the same site the write data and information for order assurance by synchronous remote copy.

1 .- 9 . (canceled) 
   
   
       10 . 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, said method comprising the following steps:
 said first storage system manages the setting of order assurance information to a first journal of write data, and sends the first journal including first write data and said order assurance information of said first data to said third storage system when said first storage system receives the first write data from said first computer;   said second storage system receives second write data from said second computer after receiving said first write data by said first storage system from said first computer;   said second storage system requests to said first storage system to set order assurance information of said second write data, receives said order assurance information of said second write data from said first storage system, and sends a second journal including said second write data and said order assurance information of said second write data to said third storage system;   said third storage system returns a response to said first storage system and said second storage system in parallel with each other, and writes into a storage area said first write data and said second write data based on said order assurance information included in each of the first and second journals, and   said first and second storage systems each delete said first and second journals from said first and second storage systems, respectively, when said first and second storage systems receive said response from said third storage system.   
   
   
       11 . A remote copying method according to  claim 10 , wherein said third storage system returns the response to said first storage system and said second storage system in parallel with said third storage system writing said first write data and said second write data into said storage area. 
   
   
       12 . A remote copying method according to  claim 11 , wherein before writing the first and second write data into the storage area, the third storage system stores the first and second journals therein, and after writing the first and second write data into the storage area, the third storage system deletes the first and second journals. 
   
   
       13 . A remote copying method according to  claim 12 , wherein the steps of sending the first and second journals from the first and second storage systems, respectively, to the third storage system, storing the first and second journals in the third storage system, storing the first and second write data in the storage area, and deleting the first and second journals; are performed in parallel with the steps of returning a response to the first and second storage systems by the third storage system, and deleting the first and second journals by the first and second storage systems, respectively. 
   
   
       14 . A remote copying method according to  claim 10 , wherein the storing into the storage area of said first write data and said second write data is performed by referring to a reflect flag for each of the first and second write data contained in the first and second journals, respectively; extracting the first and second write data from the first and second journals, respectively, whose reflect flags are OFF, in the order set by said order assurance information included in each of the first and second journals, and after storing the first and second data in the storage area, the third storage system sets ON the reflect flags for the first and second write data. 
   
   
       15 . A system for performing asynchronous remote copying between a first site and a second site, comprising:
 a first storage system in said first site coupled to a first computer, and a second storage system in said first site coupled to a second computer; and a third storage system in said third site;   wherein said first storage system manages the setting of order assurance information to a first journal of write data, and sends the first journal including first write data and said order assurance information of said first data to said third storage system when said first storage system receives the first write data from said first computer;   wherein said second storage system receives second write data from said second computer after receiving said first write data by said first storage system from said first computer;   wherein said second storage system requests to said first storage system to set order assurance information of said second write data, receives said order assurance information of said second write data from said first storage system, and sends a second journal including said second write data and said order assurance information of said second write data to said third storage system;   wherein said third storage system returns a response to said first storage system and said second storage system in parallel with each other, and writes into a storage area said first write data and said second write data based on said order assurance information included in each of the first and second journals, and   wherein said first and second storage systems each delete said first and second journals from said first and second storage systems, respectively, when said first and second storage systems receive said response from said third storage system.   
   
   
       16 . A system for performing asynchronous remote copying according to  claim 15 , wherein said third storage system returns the response to said first storage system and said second storage system in parallel with said third storage system writing said first write data and said second write data into said storage area. 
   
   
       17 . A system for performing asynchronous remote copying according to  claim 16 , wherein before writing the first and second write data into the storage area, the third storage system stores the first and second journals therein, and after writing the first and second write data into the storage area, the third storage system deletes the first and second journals. 
   
   
       18 . A system for performing asynchronous remote copying according to  claim 17 , wherein the third storage system sends the first and second journals from the first and second storage systems, respectively, to the third storage system, stores the first and second journals in the third storage system, stores the first and second write data in the storage area, and deletes the first and second journals; in parallel with returning a response to the first and second storage systems, and deleting the first and second journals by the first and second storage systems, respectively. 
   
   
       19 . A system for performing asynchronous remote copying according to  claim 15 , wherein the storing into the storage area of said first write data and said second write data is performed by the third storage system by referring to a reflect flag for each of the first and second write data contained in the first and second journals, respectively; extracting the first and second write data from the first and second journals, respectively, whose reflect flags are OFF, in the order set by said order assurance information included in each of the first and second journals, and after storing the first and second data in the storage area, the third storage system sets ON the reflect flags for the first and second write data.