iSCSI - The demise of the Fibre diet?
Not too long ago, if you were talking about SAN, Fibre Channel was likely included somewhere in the conversation. Fiber Channel has been the mainstay for connecting devices to a SAN, though its popularity may be due more to a lack of choice rather than any other factor.
Although widely adopted, Fibre Channel has long been criticized for its implementation difficulty, compatibility issues and immature management tools. And that's only part of the story. The cost of a Fibre Channel solution is still high, coming in at an estimated staggering $1000 per port, with no sign that the per-port implementations costs are going to drop drastically any time soon.
The question then becomes, is there a method to connect devices to a SAN that avoids the associated costs of a Fibre Channel solution and addresses some of its shortfalls? The answer would appear to be yes. A newer solution, IP storage, has emerged and promises to become a viable mass-market loosening the grip of the often costly and cumbersome Fibre Channel solutions.
As the accepted standard for moving data across the network, it was really only a matter of time before TCP/IP became a more active component in the storage industry. Although it is only one of the competing standards that implements storage over IP, iSCSI (Small Computer Systems Interface over IP) seems poised to be the future system of choice for IP based storage transport. In the same way that Fibre Channel provides a mechanism for transporting data over dedicated fibre links, iSCSI provides a method for transmitting data between iSCSI devices. The difference is that iSCSI, by using TCP/IP, encapsulates SCSI data traffic and transports it over any TCP/IP network.
The key to iSCSI's potential success hinges on the fact that it is able to provide storage networking by sending packets and SCSI commands over any existing IP network including the Internet. IP storage options like iSCSI utilize existing Ethernet infrastructure allowing Storage Area Networking to be implemented in a much larger market which has previously found fibre Channel solutions simply too expensive. With the increasing popularity of Gigabit Ethernet, iSCSI becomes increasingly attractive to small and mid-sized organizations where the high-ticket price of Fibre Channel is simply not an option. In a nutshell, iSCSI maintains all of the manageability, cost effectiveness, versatility and compatibility that put Ethernet networking on the map in the first place.
The ability to use existing Ethernet infrastructure such as hubs and switches can be seductive but its just the tip of the savings iceberg. Because iSCSI can take advantage and use regular TCP/IP networks to transmit data, it is economically possible to implement connections and data transfers between storage devices located miles apart, connecting LANS, WANS and MANS, virtually eliminating the conventional boundaries of storage networking. Employing a similar strategy with Fibre Channel is cost prohibitive.
Boosting the validity of iSCSI as a viable storage strategy is the number of key companies developing technologies to support it. IBM has introduced the 4125 family of iSCSI devices, Adaptec has EtherStorage, their family of iSCSI compliant products, and the introduction of the SN 5420 Storage Router brings Cisco into the middle of the iSCSI arena. With such high profile IT organizations investing time, money and resources, the future of iSCSI seems bright indeed but it doesnt have it all its own way.
In terms of pure performance, Fibre, with speeds soon to reach 2Gbps will most certainly be faster than iSCSI, giving it a clear advantage. This single fact will ensure that fibre has a continuous, and large, foothold in network storage. Quite simply, iSCSI may be changing the landscape of storage networking but Fibre does not appear to be going anywhere just yet. Storage over IP and iSCSI are in their infancy and although it has the potential to have a huge impact on the storage industry, it is not positioned to usurp Fibre just yet. Having said that, if iSCSI turns out to be as successful as predicted, the demand for Fibre could be restricted to those companies who are willing to pay for the performance Fibre Channel provides.
Of course there is no reason why Fibre and iSCSI cannot coexist in storage area networking solutions and whichever emerges the winner, it is sure to bring the advantages of storage area networking to a much larger audience.