The Growing Use Of IP Networks To Connect SANs

The massive shift in business toward electronic transactions has built momentum for high-availability storage. Consequently, vendors in the storage market are developing and shipping a variety of applications designed to enable business continuance solutions in storage environments. Applications from vendors such as Compaq, EMC, Hitachi Data Systems, and VERITAS Software have achieved great penetration into the data center. Each of these applications can insure the security of data stored remotely, typically by connecting SANs (storage area networks) in the primary data center to those in a remote backup site.

SAN extension is a key element in many business continuance methodologies and has, until very recently, largely been performed over ATM (asynchronous transfer mode), dark fiber, or DWDM (dense wavelength division multiplexing) links between the sites. While ATM solutions work over longer distances and are available in most business centers in North America, they are often limited in speed to OC3 rates (155 megabits per second [Mbps]) and have high latency. Dark fiber and DWDM solutions are the most expensive but also have the highest possible throughput for storage applications. DWDM offers the additional benefit of being able to send multiple full-speed data streams on a single fiber optic cable.

Now a new breed of technologies, represented by managed IP (Internet protocol) networks and Fibre Channel over IP gateways, offers new and compelling options for SAN extension. IP sits on top of Ethernet and has been almost exclusively adopted as the protocol of choice for communication between networked systems. Advances in Ethernet switch/router design and processing speeds and the reduction in cost through advanced circuit design allow for truly high-speed applications to run over IP/Ethernet links.

Metro Ethernet Combines Flexibility, Ease Of Administration
Following right behind the aforementioned technological advances is a new class of connectivity: metro Ethernet. Led by companies like Yipes, Telseon, and Cogent, metro Ethernet data carriers offer data links in metropolitan areas that look and feel like LAN connections but offer data transfer speeds of up to 1 gigabit per second. These new carriers offer exceptional service but may have only a limited service area.

Traditional data carriers such as AT&T, WorldCom, Sprint, and Qwest also offer products that present the end user with an Ethernet port to connect to their networks, but with a much larger footprint. To fill gaps in their service and connectivity between metros, the younger companies have teamed up with these established players to offer competitive services.

Metro Ethernet connectivity offers four key benefits. First, these connections are generally available in 1 Mbps increments for very competitive prices - as little as $1,000 per month for a 100 Mbps link. Second, several of the vendors allow the customer to vary the link speed for short periods (for example, to allow a database replication/synchronization between two sites) as opposed to the conventional fixed "peak bandwidth at a fixed cost" approach. Third, these new services can be purchased with service level agreements that specify the acceptable latency, data loss (bit error rate), and downtime - all critical pieces to a server-storage environment. Finally, metro Ethernet connectivity imposes no new management schema upon the end user. The circuits are set up, monitored, and managed using tools the LAN administrator is already familiar with.

IP-SAN gateways and switches leverage the combined benefits of Fibre Channel SANs and IP networks, providing seamless connectivity between sites and unifying multisite SANs under a single management scheme. In other words, these products extend well-engineered, well-understood Fibre Channel storage systems over widely deployed technologies - Ethernet and IP.

With the right equipment in a solution provider's line card, remote data applications are being installed now. Solutions providers are in the best position to capitalize on high-revenue, remote storage application solutions.