Patent ID: 6173377
Filing Date: 2001-01-09
Classification: G06F,G11B,H04L,Y10S

Abstract:
A data storage system for providing remote data copying, said data storage system comprising:a first data storage subsystem including first data storage, anda second data storage subsystem including second data storage, the second data storage subsystem being at a location remote from the first data storage subsystem, andat least one data link between the first data storage subsystem and the second data storage subsystem for transmission of remote copy data from the first data storage subsystem to the second data storage subsystem, and for transmission of remote copy data from the second data storage subsystem to the first data storage subsystem;wherein the first data storage includes a first set of primary storage locations, and the second data storage includes a first set of secondary storage locations corresponding to the first set of primary storage locations; and the second data storage includes a second set of primary storage locations, and the first data storage includes a second set of secondary storage locations corresponding to the second set of primary storage locations; andwherein said first data storage subsystem maintains a first indicator providing an indication of whether a first specified data element stored in said first set of primary data storage locations is valid, a second indicator providing an indication of whether a valid secondary copy of said first specified data element is stored in said first set of secondary data storage locations, a third indicator providing an indication of whether a write is pending of said first specified data element to said first set of primary data storage locations, and at least a fourth indicator providing an indication of whether a write is pending of said first specified data element to said first set of secondary data storage locations, andwherein said second data storage subsystem maintains a fifth indicator providing an indication of whether a second specified data element stored in said second set of primary data storage locations is valid, a sixth indicator providing an indication of whether a valid secondary copy of said second specified data element is stored in said second set of secondary data storage locations, a seventh indicator providing an indication of whether a write is pending of said second specified data element to said second set of primary data storage locations, and at least an eighth indicator providing an indication of whether a write is pending of said second specified data element to said second set of secondary data storage locations.