Dell SRDF Introduction

Three-site configurations

Table 1. SRDF multisite solutions This table shows the three-site configurations for SRDF.
Solution highlights	Site topology
Concurrent SRDF Three-site disaster recovery and advanced multisite business continuity protection. Data on the primary site is concurrently replicated to two secondary sites. Replication to a remote site can use SRDF/S, SRDF/A, or adaptive copy.
Cascaded SRDF Three-site disaster recovery and advanced multisite business continuity protection. Data on the primary site is synchronously mirrored to a secondary (R21) site. The data is then asynchronously mirrored from the secondary (R21) site to a tertiary (R2) site. The first “hop” is SRDF/S. The second hop is SRDF/A.
SRDF/Star Three-site data protection and disaster recovery with zero data loss recovery, business continuity protection, and disaster-restart. Available in two configurations: Cascaded SRDF/Star Concurrent SRDF/Star Differential synchronization allows rapid reestablishment of mirroring among surviving sites in a multisite disaster recovery implementation. Implemented using SRDF consistency groups (CG) with SRDF/S and SRDF/A.
SRDF/Automated Replication (SRDF/AR) Combines SRDF and TimeFinder to optimize bandwidth requirements and provide a long-distance disaster restart solution. Operates in three-site solutions that use a combination of SRDF/S, SRDF/DM, and TimeFinder. SRDF/AR is available only for arrays that run Enginuity 5876 since it uses STD (thick) devices. Arrays that run PowerMaxOS 10 (6079), PowerMaxOS 5978 and HYPERMAX OS 5977 have TDEV (thin) devices only.