Patent ID: 7111004

Claim:
A computer implemented method for mirroring data, comprising: establishing a relationship between a plurality of source data units in a primary storage and a plurality of corresponding target data units in a secondary storage; initiating an operation to perform an initial copy of all source data units in the relationship to corresponding target data units; receiving an update to a source data unit; determining whether a first write mode is indicated; copying the update to the source data unit in the first write mode to the corresponding target data unit if the first copy write is indicated; copying the update to the source data unit to the corresponding target data unit in a second write mode if the first write mode is not indicated; if the first write mode is not indicated, then determining whether a number of writes for all data units subject to the relationship falls below a threshold; and indicating the first write mode if the number of writes for all data units subject to the relationship falls below the threshold.