12
FCoE and iSCSI: Where,When
and Why
David Dale, Chair SNIA IP Storage Forum
UM SNIA
FOR
IP
Introduction and Pause. It’s not clear to me why anyone would want
When new technologies are in development we often to do this – i.e., run an Ethernet network without also
SNIA
see articles by analysts and media pundits predicting supporting TCP/IP traffic, when we already have Fibre
wholesale change, as the emerging new technology Channel.
enters the market. This is often portrayed as a head-to-
head battle with an existing technology – a fight to the For “converged” networks - i.e., also running TCP/IP - it
death. Unfortunately, this impression is usually the depends on a new set of Ethernet capabilities that have
result of briefings by vendors with a big stake in the collectively become known as “Data Center Bridging”
new technology, without much consideration of the IT (DCB) to provide a transport suitable for Fibre Channel
realities. It shouldn’t be surprising then that in the real traffic. Fibre Channel frame transmission requires a
world, technology uptake rarely happens that way. In “lossless” transport environment, so the IEEE 802.1 DCB
most cases, the new technology coexists with other Working Group is defining some extensions to Ethernet
technologies for an extended period of time, as each to provide this: Priority-based Flow Control, Enhanced
finds its place in the market. A case in point is the forth- Transmission Selection, and Congestion Notification
coming emergence of Fibre Channel over Ethernet (which is optional for initial FCoE deployment). These
(FCoE), which has already been written about as an specifications are expected to be completed by the sec-
iSCSI killer. This article examines iSCSI and Fibre ond half of 2009.
Channel SAN market today, and where different option
fit. It goes on to suggest where FCoE solutions are most The implications of FCoE for customers are all positive.
likely to fit – and why IT organizations may choose You can confidently buy Fibre Channel solutions today,
them. and have the option in the future of either following the
Fibre Channel bandwidth roadmap to 8Gbit and beyond,
About FCoE or of moving to a 10 Gigabit Ethernet “converged” fab-
So what is FCoE? Well, it’s a new protocol specification, ric for the data center, with minimal disruption to your
being developed in the INCITS T11 committee. FCoE existing Fibre Channel hardware (HBAs and arrays), fab-
enables Fibre Channel commands to be transmitted ric management and storage admin knowledge base.
natively over Ethernet by using an optional transport iSCSI, in contast to FCoE, is a standard SAN protocol
mechanism instead of TCP/IP. FCoE is designed to main- designed to transport SCSI block storage commands
tain backward compatibility with existing Fibre Channel over Ethernet using TCP/IP. iSCSI was designed to take
endpoint infrastructure, and it’s targeted at data center advantage of all the ease-of-use, high availability and
SANs using a “converged” 10 Gigabit Ethernet network guaranteed delivery mechanisms provided by TCP/IP,
infrastructure. The specification is expected to enter while providing a seamless path from 1Gigabit Ethernet
standards ratification in the Spring of 2009. to 10 Gigabit Ethernet and beyond. iSCSI mostly runs
on Gigabit Ethernet networks today, though we have
For FCoE-only networks, FCoE depends on existing seen 10 Gigabit iSCSI deployments over the past couple
optional Ethernet capabilities, such as Jumbo Frames of years. It’s worth noting here that Ethernet assumes
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