Dell PowerFlex 4.5.x Technical Overview

Storage data replicator

Storage data replicators (SDRs) process all I/Os of replication volumes.

The source SDRs processes all application I/Os of replicated volumes. At the source, the SDC sends application I/Os to the SDR. The I/Os are sent to the target SDRs and stored in their journals. The journals of the target SDRs 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.

The source SDR processes all application I/Os of replicated volumes. The source SDR saves changes to the journal, and later sends them to the target SDRs. At the target, the SDRs receive the changes, and when a consistent image is available, apply the changes to the target volumes.

A minimum of two SDRs are deployed at the source and target protection domain to ensure high availability.

The ratio of SDRs in a source protection domain to the SDRs in its target protection domain is limited. The maximum ratio of peer SDRs is 1:6, and the maximum ratio of SDRs in maintenance is 1:18. The Add_SDR and Remove_SDR commands fail if the operation results in an unsupported ratio. If the SDRs ratio exceeds the allowed value as a result of a failure or planned maintenance, the Add_RCG command fails. Existing RCGs and replication operations are not impacted.