The technology lets blocks of storage data be transported over Gigabit Ethernet and is easier and less expensive to install than Fibre Channel. Because it runs over Gigabit Ethernet networks, iSCSI doesn’t require host bus adapters in servers and Fibre Channel switches. Nor do IT administrators, for the most part, need to have special knowledge and training in storage technology to deploy iSCSI.
According to IDC, while iSCSI today accounts for only a 3% share of external disk storage, the research firm expects it to reach more than 20% by 2010. Lower costs and iSCSI’s ease of management are among the factors driving adoption. “We are seeing increasing demand for iSCSI SAN storage. iSCSI is excepted to have one of the highest compound SAN storage growth rate (according to IDC). The driving factor for growth of this market is in the Small to Medium Business Market,” says Walid Gomaa, StorageWorks Business Unit Manager, Hewlett-Packard Middle East.
Introduced on 100Mb Ethernet, iSCSI gained popularity with the broad adoption of Gigabit Ethernet. iSCSI now supports 10-Gigabit Ethernet for high-bandwidth applications particularly in business-critical Windows environments, where iSCSI is very broadly deployed and viewed as a mainstream SAN solution in both small/medium and in large organizations. In addition, the recent rapid growth of iSCSI solutions for virtual server and blade server environments has made iSCSI the fastest growing segment of the storage market and has approached a US$1 billion market. That growth is expected to continue in the coming years as virtual server environments further proliferate, and as 10 Gigabit Ethernet drives the technology into large-scale, high-performance, and tier 1 data center environments. “We see the key drivers being cost, as iSCSI utlises commodity IP infrastructure as opposed to expensive HBAs required by FB and training. iSCSI offers greater simplicity in implementation than FC and leverages the existing skill sets of in-house network administrators. Learning iSCSI can be accomplished with some online research and maybe a web-based class. FCP, however is nothing like TCP/IP over Ethernet and requires some intensive, specialized training. From a labor perspective, you will most likely pay more for the skills required to implement and maintain a large FC/SAN than a large IP network,” says Martyn Molnar, Sales Manager-Middle East, NetApp.
Simplicity is another factor in favour of IP storage. Maintaining a single IP network infrastructure that powers both production and storage networks is far easier than maintaining 2 separate technologies. Also, storage admins in FC/SAN environments often manage the storage network in addition to the arrays and host HBAs. In many IP Storage environments, the IP network team manages both the production IP network and the IP storage network. This allows storage admins to focus their efforts on host and array connectivity and allows for faster provisioning, as there is less of a need to touch the network for zone management.
However, on the high end, Fibre Channel still reigns as the king of enterprise storage-area-network technologies. It's fast, it can handle long distances, and it's got strong vendor support. ISCSI, however, is the heir apparent. When it comes to new SANs, add-ons to existing systems or departmental-level installations at large enterprises that have Fibre Channel, customers increasingly are choosing iSCSI.
“FC SANs are still the predominant storage infrastructure in large enterprises, although the growth rates are on the decrease. FC SAN’s are often chosen when performance is the top criterion. However if performance requirements aren't ridiculous, iSCSI SAN presents a very interesting alternative, “ says Molnar. For example, 1-4 Gigabits/sec per host would be easily accommodated while higher requirements can always be met with proper engineering. The only exception would be when extremely high latency requirements are needed and when cost is not a deciding factor. NetApp believes performance will continue to improve since iSCSI follows the Ethernet standards road map, which will include 40 gigabit and 100 gigabit in the near future. As the functionality of Ethernet continues to increase, its value as a data network continues to expand. The next generation of Ethernet includes enhancements delivered with DCB that are ideally suited for storage networks, he adds.
Gomaa offers another perspective: “The performance of the iSCSI is highly dependent on the network bandwidth and latency. The good news for the iSCSI environment is the continuous growth in the Ethernet bandwidth (1G GbE, 10 GbE). FC SAN environments have dedicated FC network which eliminate the dependency on Ethernet network performance. In a typical FC SAN environment, there are MANY more disks being served by a set of network connections than with a ISCSI SAN. It is not really fare to compare the two technologies in performance.”
But even after giving Fibre Channel its due, the consensus is that iSCSI is the ultimate winner.
Analysts and users cite the upfront cost of Fibre Channel components, but stress that specialized expertise continues to be a problem. Another iSCSI plus is that such important features as data replication and snapshots have been à la carte menu items in the Fibre Channel realm but are part and parcel of iSCSI.
IT experts also say that with implementation know-how, iSCSI can rival current Fibre Channel speeds.
Storage analysts see the writing on the wall. “We believe that iSCSI will be the dominant SAN interconnect over time,” the Enterprise Strategy Group's analyst Tony Asaro says. “Although Fibre Channel is the leading storage-networking interconnect, it is not ubiquitous because ultimately, it is expensive and complex.” Companies that have implemented it see the value in terms of performance and reliability. “However, Fibre Channel has not reached universal adoption and therefore requires either complementary or replacement technology. This is where iSCSI plays a vital role,” he says.