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Friday, October 31st, 2014

SAN management

iSCSI versus FCoE: which standard is winning the war?

As organizations look for ways to lower costs, while still gaining from the benefit of shared storage technology, the choice between an iSCSI and FCoE solution continues to be pitted in IT boardrooms. Both ride on the Ethernet - delivering faster, more reliable performance. Both are robust and highly reliable. And both simplify data management while maximizing storage utilization.

What should organizations look for when choosing between iSCSI and FCoE solutions? What are the key differences between these two standards? Which will give better performance when high throughput and low latency are critical to organizations? Is the industry beginning to choose one over the other? How will both standards evolve to accommodate demands in the future? Will FCoE become the next FC-SAN?

In search of answers to these questions, we asked David Dale, NetApp's industry standards director and chair of the SNIA Ethernet Storage Forum, for his views.

What should organizations look for when choosing between iSCSI and FCoE solutions?
Dale: The first thing to look at is the current IT environment. iSCSI deployments to date have typically been in tier 2 and tier 3 data centers in large organizations; in the core data center of small/medium enterprises; and in remote offices. iSCSI is often chosen as a shared storage solution in these environments because Fibre Channel has had difficulty penetrating them due to issues around cost, complexity, and the availability of knowledgeable admin staff.

On the other hand, FCoE is usually chosen in existing Fibre Channel SAN environments (typically tier 1 and tier 2 data centers in large and medium organizations) where the customer explicitly wants to move to a unified network fabric based on 10Gb Ethernet. FCoE enables the customer to make a fairly easy transition to Ethernet without impacting their existing investment in Fibre Channel storage systems and Fibre Channel SAN management expertise. FCoE is designed specifically to maintain backward compatibility with existing Fibre Channel endpoint infrastructure.

What are the key differences between these two standards?
Dale: iSCSI is a mature industry standard SAN protocol designed to transport SCSI block storage commands over Ethernet using TCP/IP. In other words it delivers SAN over TCP/IP.

FCoE, in contrast, is a new industry standard SAN protocol designed to transport Fibre Channel frames (which contain SCSI block storage commands) over Ethernet using an optional transport mechanism instead of TCP/IP. This optional transport mechanism (usually referred to as Data Center Bridging) provides a transport suitable for Fibre Channel traffic (which cannot tolerate dropped frames) via several Ethernet extensions: priority-based flow control, enhanced transmission selection, and congestion notification.