Tertiary storage unit management in bidirectional data copying

摘要

In one embodiment of the present description, mirroring is provided for a pair of storage units in bidirectional synchronous mirror relationships, and a tertiary storage unit. The mirroring includes multi-target mirroring to write updates written to the first storage unit to both the second storage unit and to a third storage unit. Similarly, for updates written to the second storage unit, multi-target mirroring is employed to write those to both the first storage unit and to the third storage unit. Other aspects are described.

主权项

1. A method, comprising:
writing updates to a first storage unit so that the first storage unit has updates prior to a second storage unit; writing updates to the second storage unit so that the second storage unit has updates prior to the first storage unit; multi-target mirroring updates written to the first storage unit, to both the second storage unit and a third storage unit; and multi-target mirroring updates written to the second storage unit, to both the first storage unit and the third storage unit; wherein the multi-target mirroring updates written to the first storage unit, to both the second storage unit and a third storage unit includes:
establishing a mirroring relationship from the first storage unit to the second storage unit;establishing a mirroring relationship from the first storage unit to the third storage unit;copying the first storage unit to the second storage unit; andcopying the first storage unit to the third storage unit; andwherein the multi-target mirroring updates written to the second storage unit, to both the first storage unit and the third storage unit includes:establishing a mirroring relationship from the second storage unit to the third storage unit; andestablishing a mirroring relationship from the second storage unit to the first storage unit; the method further comprising:
detecting a failure of the mirroring relationship from the first storage unit to the third storage unit;in response to the failure detection, suspending the mirroring relationship from the second storage unit to the third storage unit;detecting that the third storage unit is not synchronized to the first and second storage units; andin response to the non-synchronized detection:
suspending the mirroring relationship from the first storage unit to the third storage unit;suspending the mirroring relationship from the second storage unit to the first storage unit;shifting the writing of updates so that updates are written to the first storage unit so that the second storage unit no longer has updates prior to the first storage unit,resynchronizing from the first storage unit to the third storage unit; andre-establishing the mirroring relationship from the first storage unit to the third storage unit; andre-establishing the mirroring relationship from the second storage unit to the first storage unit.