Fibre Channel SAN and iSCSI have often been positioned as two competing technologies dueling each other for market share. FC SAN, though relatively mature, is expensive and more complex to implement. iSCSI, while low-cost and easy to manage, is a newer technology. Though Fibre Channel SANs are more prevalent today, iSCSI has been gaining ground and penetrating companies of all sizes.
FC SAN and iSCSI SAN: Pros and Cons
As the name implies, both Fibre Channel SANs and iSCSI SANs are storage area networks. Using a SAN, an enterprise can consolidate its storage resources and provision them to servers according to need. Business continuity is also best served by a SAN. SANs ensure that duplicate copies of the data are contained in different storage arrays or even at different data warehouse locations to allow for disaster recovery. SANs also complement any investment in server virtualization, as many server virtualization features actually require SAN storage.
FC SANs are dedicated storage networks, whose deployment requires specialized host bus adapters, specialized FC switches and FC storage arrays. Although all of these components are costly and add a layer of complexity, companies have been willing to pay this premium to gain the reliability and performance of FC SAN. However, unable to afford this for every server in the enterprise, most companies connect only those servers with the highest storage demands to their FC networks. This often results in a situation where the majority of servers within an enterprise are stranded with only direct attached storage and no networked storage services.
On the other hand, iSCSI SANs are based upon Ethernet technology, which is well-understood and inexpensive to deploy. A key advantage, therefore, is that iSCSI SANs can easily be connected to any server. However, iSCSI SANs are relatively new to the market compared to Fibre Channel, and many customers are hesitant to migrate from their existing tried and tested solution. Furthermore, as the newer technology, iSCSI has had to prove itself capable of the throughput requirements of enterprise environments. Recent advancements in iSCSI initiators and TOE cards have made dramatic improvements in iSCSI performance. With 10 GB Ethernet becoming more pervasive, the debate about iSCSI vs. FC performance will subside.
Although both Fibre Channel and iSCSI SANs employ the same block level SCSI commands as their basis, until recently it has been very difficult to combine the technologies at one site. Enterprises with heavy investment in FC SAN infrastructure could not easily integrate an iSCSI SAN into their environment. Against their better instincts IT departments were forced to make a choice: Am I an iSCSI SAN or an FC SAN shop?
This limitation has recently been removed with the introduction of intelligent network switches that could extend existing FC SANs with iSCSI connectivity. By placing the network management intelligence in the network switches, enterprises can now have the benefit of iSCSI connectivity to the servers, while still making use of all the benefits of FC connectivity at the storage side.
Virtualization with FC and iSCSI SAN
Server virtualization affords users many benefits including consolidation of server resources and business continuity assurance at the application level. In a consolidated server environment, when something bad occurs to a specific physical server, all the virtual machines that ran on it can simply be moved and started up on a different physical server. Similarly storage virtualization completes the benefits of server virtualization at the storage level. Storage virtualization consolidates storage resources and provides the assurance that not only will applications be able to run on the new physical servers, they will also be able to access their storage from this new location.
A common challenge that IT managers face is choosing which storage SAN (FC or iSCSI) to adopt for their virtualization initiative.
Until recently, enterprises with large FC SAN investments had to decide between two options. On the one hand, they could interconnect their new consolidated servers to their existing SANs using FC technology. They would benefit from the use of their existing storage environment and its services. However, the connectivity costs for interconnecting servers to FC SAN are very high. This cost factor is a major barrier in server consolidation projects whose main purpose is to save costs, not to create larger expenditures. This option also locks users to FC technology, closing the door to future migration to new, less expensive technologies.
On the other hand, enterprises had the choice of creating new separated iSCSI SANs for their consolidated server environment. Under this scenario, they benefit from simple low-cost server connectivity, but are forced to throw away their investment in FC storage and FC SAN storage services software.
There is now a third option that provides enterprises with the best of both worlds. Using intelligent network switches that support both iSCSI server connectivity and FC storage connectivity (such as the SANRAD V-Switch), organizations can leverage their prior FC storage investments and, at the same time, take advantage of the full benefit of low-cost iSCSI server connectivity. Such a solution architecture (as shown in Figure I) also enables enterprises to maintain full freedom to choose the best storage to meet their future requirements.
The future of Fibre Channel and iSCSI SAN
As it looks right now both FC and iSCSI SANs will continue to be integral parts of a storage infrastructure for many years. Fibre Channel will continue to be a major force within large enterprises for a number of reasons. It is already there: the investment, the tools, and the knowledge. iSCSI will continue to gain popularity but co-exist with Fibre Channel.
Intelligent integrated switches create an ideal environment for the co-existence of FC and iSCSI. With intelligent integrated switches, enterprises gain the best of both worlds and can deploy key applications such as instantaneous disaster recovery and non-disruptive data migration with any vendor's storage. The open architecture of intelligent switches also eliminates the extra hardware and software costs of proprietary storage implementations.
By Dr. Allon Cohen, Vice President of Product Management, SANRAD (www.sanrad.com)
