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SRDF/Metro is a mode of SRDF which provides active/active access to the R1 and R2 of an SRDF configuration. In traditional SRDF, R1 devices are Read/Write accessible while R2 devices are Read Only/Write Disabled. In SRDF/Metro configurations both the R1 and R2 are Read/Write accessible. The way this is accomplished is the R2 takes on the personality of the R1 in terms of geometry and most importantly the WWN. By sharing a WWN, the R1 and R2 appear as a shared virtual device across the two arrays for host presentation. A host, or typically multiple hosts in a cluster, can read and write to both the R1 and R2. SRDF/Metro ensures that each copy remains current and consistent and addresses any write conflicts which might arise. A simple diagram of the feature is available in Figure 1. SRDF/Metro
SRDF/Metro Smart DR, or MetroDR, is a two-region high available (HA) disaster recovery (DR) solution. It integrates SRDF/Metro and SRDF/A enabling HA DR for a Metro session. Both Metro sites are capable of sending updates to the third site so that if one Metro leg fails, the other continues to operate and update the DR site. A simple diagram of the feature is available in Figure 2.
The SRDF/Metro feature provides the following advantages: