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Synchronous SRDF (SRDF/S) is a method of replicating production data changes from locations less than 200 km (124.27 mi) apart. Synchronous replication takes writes that are inbound to the source PowerMax and copies them to the target PowerMax. The resources of the storage arrays are exclusively used for the copy. The write operation from the virtual machine is not acknowledged back to the host until both PowerMax arrays have a copy of the data in their cache. See the Dell support site for more information about SRDF/S.
Figure 177 is a schematic representation of the business continuity solution that integrates a VMware environment and SRDF technology. The solution shows two virtual machines accessing devices on PowerMax storage arrays on the production site. The boot virtual devices (VMDKs) are stored on VMFS, while the data LUNs are RDMs. On the disaster recovery site (DR), those same devices are read-only. If a failure occurs, the VMs in the schematic would be registered and powered on, which explains their ghostly placeholder status. However, while there is no disaster, the resources at the DR site are used as a test environment. This task is accomplished through TimeFinder/SnapVX. SnapVX snapshots of the R2 read-only devices are taken and then linked to read/write devices which are presented to the VMware environment at the DR site. The VMs are registered and if there is no disaster, the compute and array resources do not remain idle and serve as the test environment.
Note: As most customers present R2s to the DR site, be sure to review Detaching the remote volume.