Fan-out asynchronous replication logical level caching

A computer program product including a non-transitory computer readable storage medium having computer program code encoded thereon that when executed on a processor of a computer causes the computer to operate a storage system, the computer program product comprising:

• computer program code for responding to a request to replicate one or more pages of data from a production system to a plurality of target systems, wherein the replication of the pages of data to the plurality of target systems is associated with a corresponding replication session to each of the plurality of respective target systems, wherein the production system comprises a processor having access to a memory and to a physical cache, wherein the physical cache is configured for storing a plurality of pages of data needed for the replication of the one or more pages of data to the plurality of target systems, each respective page of data having a respective hash signature computed based on the respective page of data and a respective hash handle that is used to access the respective hash signature;
• computer program code for determining, for each of the one or more pages, a total number of corresponding replications needed to replicate the respective page of data to the plurality of target systems;
• computer program code for establishing the corresponding replication session for each of the plurality of target systems;
• computer program code for receiving a request for the respective page of data based on a first hash handle;
• computer program code for determining a type of the received request, wherein the type indicates whether the request is for one of a replication session and a non-replication session;
• computer program code for determining if it is the first time the first hash handle has been requested, and if it is the first time the given hash handle has been requested then:
• computer program code for retrieving the respective page of data associated with the first hash handle;
• computer program code for storing the respective page of data in a physical cache;
• computer program code for dynamically tracking when each of the corresponding replication sessions requests the respective page of data based on the first hash handle, to determine when the total number of corresponding replications has taken place, wherein, as part of the dynamic tracking, request types corresponding to non-replication sessions are not counted towards the total number of corresponding replications;
• computer program code for determining if it is not the first time the first hash handle has been requested, and if it is not the first time the first hash handle has been requested, then:
• computer program code for retrieving the respective page of data from the physical cache;
• and
• computer program code for clearing the respective page of data from the physical cache when all of the corresponding replication sessions have requested the respective page of data based on the first hash handle, based on the dynamic tracking;
• and
• computer program code for clearing the respective page of data from the physical cache when a determination is made that at least one of the following conditions exists:
• all of the corresponding replication sessions that require the respective page of data in the physical cache, have accessed the respective page in the physical cache and the total number of corresponding replications has been reached;
• wherein at least one of the determination of the type of received request, the dynamic tracking of the requests for the respective page of data and the clearing of the respective page of data from the physical cache, is configured so that the processor requires only one physical cache to respond to the request to replicate the one or more pages of data from the production system to the plurality of target systems.

A system, comprising;

• a processor;
• and
• a non-volatile first memory in operable communication with the processor and storing computer program code that when executed on the processor causes the processor to execute a process operable to perform the operations of:
• responding to a request to replicate one or more pages of data from a production system to a plurality of target systems, wherein the replication of the pages of data to the plurality of target systems is associated with a corresponding replication session to each of the plurality of respective target systems, wherein the production system comprises a processor having access to a second memory and to a physical cache, wherein the physical cache is configured for storing a plurality of pages of data needed for the replication of the one or more pages of data to the plurality of target systems, each respective page of data having a respective hash signature computed based on the respective page of data and a respective hash handle that is used to access the respective hash signature;
• determining, for each of the one or more pages, a total number of corresponding replications needed to replicate the respective page of data to the plurality of target systems;
• establishing the corresponding replication session for each of the plurality of target systems;
• receiving a request for the respective page of data based on a first hash handle;
• determining a type of the received request, wherein the type indicates whether the request is for one of a replication session and a non-replication session;
• if it is the first time the first hash handle has been requested, then:
• retrieving the respective page of data associated with the first hash handle;
• storing the respective page of data in a physical cache;
• dynamically tracking when each of the corresponding replication sessions requests the respective page of data based on the first hash handle, to determine when the total number of corresponding replications has taken place, wherein, as part of the dynamic tracking, request types corresponding to non-replication sessions are not counted towards the total number of corresponding replications;
• if it is not the first time the first hash handle has been requested then:
• retrieving the respective page of data from the physical cache;
• and
• based on the dynamic tracking, clearing the respective page of data from the physical cache when all of the corresponding replication sessions have requested the respective page of data based on the first hash handle;
• and
• clearing the respective page of data from the physical cache when a determination is made that at least one of the following conditions exists:
• all of the corresponding replication sessions that require the respective page of data in the physical cache, have accessed the respective page in the physical cache and the total number of corresponding replications has been reached;
• wherein at least one of the determination of the type of received request, the dynamic tracking of the requests for the respective page of data and the clearing of the respective page of data from the physical cache, is configured so that the processor requires only one physical cache to respond to the request to replicate the one or more pages of data from the production system to the plurality of target systems.