Dell PowerFlex Appliance with PowerFlex 4.x Administration Guide

The SDR RPM must be installed on all SVMs, both at the source and destination sites only if both sites have PowerFlex hyperconverged nodes. Storage Data Replicators (SDR) are responsible for processing all I/Os of replication volumes. All application I/Os of replicated volumes are processed by the source SDRs. At the source, application I/Os are sent by the SDC to the SDR. The I/Os are sent to the target SDRs and stored in their journals. The target SDRs journals apply the I/Os to the target volumes. A minimum of two SDRs are deployed at both the source and target systems to maintain high availability. If one SDR fails, the MDM directs the SDC to send the I/Os to an available SDR.