Building Disaster Recovery Serviceguard Solutions Using Metrocluster with EMC SRDF

Figure 5 Example of an M by N configuration - 2 by 1 configuration

Array

SRDF Links

R1 Vols

R2 Vols

BCVs

Node 1

Pkg A

Array

Third Location

(Arbitrators)

Node 2

Pkg B

Node 3

Node 4

Node 5

Node 6

Array

Figure 6 shows a bidirectional 2 by 2 configuration with additional packages on node3 and

node4, and R1 and R2 volumes at both data centers. In this configuration, R1 volumes and pkg

A and pkg B are at Data Center A, and R2 volumes are at Data Center B. R1 volumes for pkg

C and pkg D are at Data Center B, and R2 volumes are at Data Center A.

Figure 6 Bidirectional 2 by 2 configuration

Node 1

Array

Node 2

Array

Node 3

Node 4

Pkg C

Pkg D

BCVs

Pkg B

Pkg A

Grouping the Symmetrix devices at each data center

The use of R1/R2 devices in M by N configurations of multiple Symmetrix frames is enabled by

means of consistency groups. A consistency group is a set of Symmetrix RDF devices that are

configured to act in unison to maintain the integrity of a database. The consistency group is

implemented and managed as a single device group even though it spans multiple Symmetrix

frames because Metrocluster with EMC SRDF works at the device group level. Consistency groups

are created using either EMC PowerPath or the RDF Enginuity Consistency Assist (RDF-ECA) feature

of Solutions Enabler. In a consistency group, Symmetrix tracks the I/Os that are written to the

Setting up M by N configurations 21