During the write phase of RecoverPoint replication, when does the RPA send an acknowledgement back to the write splitter?

The RecoverPoint Appliance (RPA) acknowledges a write operation as soon as it receives the data from the write splitter. This design minimizes the performance impact on the production host. The splitter intercepts a write, sends it to both the production LUN and the RPA, and waits for an acknowledgement from both. By having the RPA acknowledge immediately upon receipt (before distribution), the splitter can quickly return the acknowledgement to the host, completing the I/O. The subsequent replication tasks, such as writing to the journal and transmitting to the remote site, occur asynchronously to the host's write operation, thus preserving application performance.

B. Waiting for the distribution phase to complete would introduce the latency of writing to the journal into the host's I/O path, which is incorrect.
C. This describes the acknowledgement path for synchronous replication at the host level, not the initial RPA-to-splitter acknowledgement, which happens much earlier.
D. Waiting for the remote RPA acknowledgement would add network latency to every production write, which is contrary to RecoverPoint's design for minimizing host impact.

1. Dell EMC RecoverPoint for Virtual Machines 5.3 Administrator's Guide. In the section "The replication process," the guide outlines the sequence of events: "3. The RecoverPoint for VMs cluster receives the write and sends an acknowledgment to the vSphere I/O filter... 6. The RecoverPoint for VMs cluster sequences and distributes the write to the journal..." This explicitly shows the acknowledgement is sent before the distribution phase. (Reference found in Chapter 1, "Introduction to RecoverPoint for Virtual Machines").

2. Dell EMC White Paper: RecoverPoint Fundamentals. This document details the I/O flow. In the section describing the write path, it states that the splitter sends the write to the production storage and the local RPA in parallel. The RPA places the write in its memory buffer and immediately sends an acknowledgement back to the splitter. This action is independent of and precedes the distribution of the write to the journal and remote RPAs. (Reference found in the "Write Path and Splitter Operation" section).