Building Disaster Recovery Serviceguard Solutions Using Metrocluster with EMC SRDF

devices. If an I/O cannot be written to a remote Symmetrix because a remote device or an RDF

link has failed, the data flow to the other Symmetrix is halted in less than one second. Once

mirroring is resumed, any updates to the data is propagated with normal SRDF operation.

Figure 7 shows how the use of consistency groups (depicted as dashed rectangle lines) ensures

that the other two links are also suspended when there is a break in the links between two of the

Symmetrix frames.

Figure 7 2 X 2 node and data center configuration with consistency groups

Node 1

Array

When these links

both go down

These links are suspended

Third Location

(Arbitrator Nodes)

Data Center A

Node 2

Node 5 Node 6

Array

Node 3

Node 4

Pkg C

Pkg DPkg B

Pkg A

Data Center B

Creating Symmetrix device groups

For each node on the R1 side (node1 and node2), create the device groups as follows.

NOTE: It is necessary to create two device groups since device groups do not span frames.

The following examples are based on the configuration shown in Figure 4.

1. Create device groups using the following commands on each node on the R1 side.

# symdg -type RDF1 create dgoraA

# symdg -type RDF1 create dgoraB

2. For each node on the R2 side (node3 and node4), create the device groups as follows. Do

the following on each node on the R2 side.

# symdg -type RDF2 create dgoraA

# symdg -type RDF2 create dgoraB

3. For each node on the R1 side (node1 and node2), assign the R1 devices to the device groups.

# symld -sid 638 -g dgoraA add dev 00C

# symld -sid 638 -g dgoraA add dev 00D

# symld -sid 130 -g dgoraB add dev 010

# symld -sid 130 -g dgoraB add dev 011

22 Configuring an application in a Metrocluster solution