Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

In a cascaded SRDF relationship, the term first hop refers to the R1-> R21 device pair, the term second hop refers to the R21->R2 device pair.

When controlling an R2 device in a cascaded SRDF relationship, the first hop represents the R2->R21 relationship and the second hop represents the R21-> R1 relationship.

Operations against one pair relationship depend on the state of the other pair relationship. The SRDF state of the R21 device in a cascaded relationship is determined as follows:

• The SRDF pair state of the R1 -> R21 device is determined by the RA status.
• The SRDF pair state of the R21 -> R2 mirror is determined by the SA status.

The following image shows how the R21 SRDF device state is determined and how each SRDF mirrored pair state is determined.

Device actions modify only the SA status of the R21 device.

For example, if rw_enable r1 is performed against the R1 -> R21 pair, and the R21 has a device SA status of WD, the overall device SRDF state is WD.

You must perform both rw_enable r1 against the R21 -> R2 pair and a rw_enable r2 against the R1 -> R21 pair to make the R21 device rw_enable to the host.

Dell Solutions Enabler SRDF Family State Tables Guide provides more information.