Verifying mirroring of source data units to target data units

A system for verifying mirroring of source data units to target data units, comprising:

• a processor;
• and
• a computer readable storage medium having program instructions executable by the processor to cause operations, the operations comprising:
• mirroring source data units in a source storage to corresponding target data units in a target storage;
• reading the source data units to compare to corresponding mirrored target data units;
• saving, in source version data, read source data units that did not match the corresponding target data units;
• rereading source data units that were read and did not match the corresponding target data units;
• and
• verifying the mirroring of the source data units in response to determining that for each mirrored source data unit, one of a read source data unit and the read source data unit saved in the source version data matches the corresponding target data unit.

A method for verifying mirroring of source data units to target data units, comprising:

• mirroring source data units in a source storage to corresponding target data units in a target storage;
• reading the source data units to compare to corresponding mirrored target data units;
• saving, in source version data, read source data units that did not match the corresponding target data units;
• rereading source data units that were read and did not match the corresponding target data units;
• and
• verifying the mirroring of the source data units in response to determining that for each mirrored source data unit, one of a read source data unit and the read source data unit saved in the source version data matches the corresponding target data unit.