Hi Alok - what is your current understanding of this concept? Knowing your current understanding will help our experienced professionals fill in the gaps.
I think, it is a replication technique held at network layer. In other techniques after disater, we can rollback to previous point in time copy which means we have some data loss. But CDP has write splitter (it splits write into two copy. one for production volume and one for journal volume) and journal volume (it is like cache. Data is written into it from write splitter and after some fixed interval data is written to replication storage array from journal volume ). any further explanation is appreciated.
Debasish Chakrabarty explains Continuous Data Protection as:
Continuous data protection (CDP) is a network-based replication solution that provides the capability to restore data and VMs to any previous PIT. Traditional data protection technologies offer a limited number of recovery points. If a data loss occurs, the system can be rolled back only to the last available recovery point. CDP tracks all the changes to the production volumes and maintains consistent point-in-time images. This makes the CDP to restore data to any previous PIT. CDP supports both local and remote replication of data and VMs to meet operational and disaster recovery respectively.
The figure portrays CDP local and remote replication operations where the write splitter is deployed at the compute system. Typically the replica is synchronized with the source, and then the replication process starts. After the replication starts, all the writes from the compute system to the source (production volume) are split into two copies. One copy is sent to the local CDP appliance at the source site, and the other copy is sent to the production volume. Then the local appliance writes the data to the journal at the source site and the data in turn is written to the local replica. If a file is accidently deleted, or the file is corrupted, the local journal enables to recover the application data to any PIT.
In case of remote replication, the local appliance at the source site sends the received write I/O to the appliance at the remote (DR) site. Then, the write is applied to the journal volume at the remote site. As a next step, data from the journal volume is sent to the remote replica at predefined intervals. CDP operates in either synchronous or asynchronous mode. In the synchronous replication mode, the application waits for an acknowledgment from the CDP appliance at the remote site before initiating the next write. In the case of asynchronous mode, the local CDP appliance acknowledges a write as soon as it is received. In case of any disaster at the source site, data can be recovered to the required PIT and the service can be restarted at the DR site.