Server Based Disaster Recovery by Making Use of Dual Write Responses

A computer program product comprising a computer readable storage medium having a computer readable program stored therein, wherein the computer readable program, when executed on a primary storage controller, causes the host primary storage controller to:

• responsive to receiving a referenced write command and a tracker write command from a host computing device, wherein the referenced write command contains data to be written to primary storage and wherein the tracker write command contains a reference to the referenced write command, create an entry in a tracker log corresponding to the tracker write command, wherein the tracker log maintains a list of tracker write commands that are not yet acknowledged to be written to a secondary storage by a secondary storage controller;
• committing the data to the primary storage;
• sending the referenced write command to the secondary storage controller for replication;
• and
• responsive to receiving an acknowledgement from the secondary storage controller for the referenced write command, erasing the entry in the tracker log and sending an acknowledgement of the tracker write command to the host computing device.

A primary storage controller comprising:

• a processor;
• and
• a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to:
• responsive to receiving a referenced write command and a tracker write command from a host computing device, wherein the referenced write command contains data to be written to primary storage and wherein the tracker write command contains a reference to the referenced write command, create an entry in a tracker log corresponding to the tracker write command, wherein the tracker log maintains a list of tracker write commands that are not yet acknowledged to be written to a secondary storage by a secondary storage controller;
• commit the data to the primary storage;
• send the referenced write command to the secondary storage controller for replication;
• and
• responsive to receiving an acknowledgement from the secondary storage controller for the referenced write command, erase the entry in the tracker log and send an acknowledgement of the tracker write command to the host computing device.

A method, in a primary storage controller, for asynchronous replication, the method comprising:

• responsive to receiving a referenced write command and a tracker write command from host computing device, wherein the referenced write command contains data to be written to primary storage and wherein the tracker write command contains a reference to the referenced write command, create an entry in a tracker log corresponding to the tracker write command, wherein the tracker log maintains a list of tracker write commands that are not yet acknowledged to be written to a secondary storage by a secondary storage controller;
• committing the data to the primary storage;
• sending the referenced write command to the secondary storage controller for replication;
• and
• responsive to receiving an acknowledgement from the secondary storage controller for the referenced write command, erasing the entry in the tracker log and sending an acknowledgement of the tracker write command to the host computing device.