Remote replication over Metropolitan Area Networks (MAN) and Wide Area Networks (WAN) has become increasingly widespread with the mass adoption and deployment of iSCSI-based storage appliances. However, despite its popularity, this activity is not bereft of challenges. One of the biggest challenges now facing replication over significant distances is the delay incurred when doing so. Signals transported at nearly the speed of light are saddled with delays, resultinging in latencies that can no longer be ignored, as is the case with LAN data transfers. These round-trip delays range from a couple of milliseconds for inter-city connections to around 80-100 ms from coast-to-coast, and as much as 250-300 ms for submarine transmissions across the globe. When geostationary satellites are used, naturally the distances covered are much greater, resulting in delays of about 700ms.

This whitepaper will examine the impact of transport distance and latency on the efficiency of network bandwidth in WAN remote replication situations over TCP/IP. It will then demonstrate how StorTrends iTX and its powerful WAN acceleration (called WDS) and deduplication technologies improve bandwidth utilization, through sophisticated compression and data reduction techniques.

Since it is founded in iSCSI technology, StorTrends relies heavily on the TCP/IP protocol, optimized for LAN for serving front-end I/Os and for synchronous replication operations. StorTrends® iTX harnesses standards- protocols to minimize the inefficiencies and high latencies of TCP/IP in WAN situations, and greatly improve data transfer speed, approaching the theoretical maximum of the connection speed. StorTrends iTX also provides performance gains through data reduction technologies such as compression and data deduplication.