Introduction
For the last decade, Fibre Channel has been the primary choice for the majority of enterprise storage
area network (SAN) infrastructures. Specifically Fibre Channel has been the default SAN technology for
many medium to large sized businesses and data centers; especially those that have high bandwidth, high
transaction, or low latency needs. Over the last six years, iSCSI has begun to carve out a market in the small
to medium sized business (SMB) computing environment while running on commodity 1 Gigabit Ethernet
networks. Although significantly slower than Fibre Channel, iSCSI has filled the needs of many SMB
environments as it has measurably lowered the cost of entry of an initial SAN purchase.
However, in recent months, the emergence of 10 Gigabit Ethernet has some enterprise users wondering if
iSCSI can now be considered for evaluation or deployment in enterprise environments. As Fibre Channel
and iSCSI are dissimilar technologies, there are several considerations that need to be discussed before
this question can be factually answered.
The Basics of iSCSI & Fibre Channel technologies:
8 Gigabit Fibre Channel
Fibre Channel began to make major inroads into enterprise storage with 1 Gigabit products that began
shipping in 1997. There have been three major performance enhancements to Fibre Channel, the most
recent being 8 Gigabit technologies.
The main concept of Fibre Channel was that it was designed to be a low latency and high performance
network storage technology. It followed the same basic operating system (OS) dynamics that had been
well established by the parallel SCSI technology, plus it had the added benefits of increased distance and
massive scalability through its networking capabilities.
The majority of Fibre Channel protocol and I/O operations are handled by a highly efficient application
specific integrated circuit (ASIC). This ASIC communicates directly with the operating system kernel via
a device driver. This efficient communication allows for native direct memory accesses (DMA) from the
SCSI layers to the host computer’s memory subsystem. In addition, the cleanliness of Fibre Channel’s
architecture, plus the protocol being managed by the ASIC allow for extraordinary I/O capabilities while
being extremely conservative in regards to CPU utilization. As Fibre Channel is CPU efficient, this allows for
more CPU cycles to be devoted to enterprise applications. Also, the above mentioned efficiencies give
an architectural advantage to Fibre Channel in terms of scalability. In other words, Fibre Channel scales in
a highly efficient manner when additional ports are added to a system.
Eight Gigabit (8 Gb/s) Fibre Channel uses an 8b/10b encoding scheme and has a single port theoretical
data transfer of approximately 800 MB/s in read or write operations or 1,600 MB/s in full duplex operations