I am planning to connect two data centres by dense wavelength division multiplexing (DWDM), and the distance between them is 70 kilometres. I am also planning to buy an EMC Symmetrix box and would like to have synchronous replication for 20% of my applications. Will the distance be an issue for synchronous replication?
The technical maximum distance for replicating data between arrays using native Fibre Channel is around 100km (although the practical and recommended safe distance for replicating data using this protocol is far less, ie less than 50Km). Using a Wave Division Multiplexing technology allows the signals to be multiplexed (joined together) at the point of transmission (or in this case at the point of array IO entry to the Dense Wave Division Multiplexer) thus expanding the total capacity bandwidth between sites. Symmetrix Remote Data Facility (SRDF)/Synchronous and DWDM has long been the choice for reliable data replication between EMC Symmetrix arrays for the more demanding of environments, although I would always recommend an analysis of an environments data profile before recommending a technology, as many other factors will affect the array's ability to transmit data over any distance.