It's raining board interconnect
switch fabrics. Or so it seems, with
last year's experimentation and
development leading to a flood of
deployments and new products.
We're seeing clusters switch gears,
going from dozens and hundreds of
nodes to thousands and tens of thousands of nodes.
Fabrics overcome many of the problems associated with buses, including
scalability, reliability, and performance.
It's relatively new technology, but the
need for speed is pushing its adoption.
Switch fabrics have finally settled into
coexistence with each other. Ethernet
remains king of the Internet and enterprise. Serial RapidIO is the platform of
choice for communications and many military applications, such as large radar system support. InfiniBand is a major player
in clustering, and PCI Express often links
them to the processors in the network.
These fabrics all have sufficient features
and performance to meet computing
needs for many years to come. Still, incremental speed jumps, as well as new features like virtual channels and remotedirect-memory-access (RDMA) support,
keep designers on their toes. Many of
these developments result from cross-pollination with other switch fabrics.
Gigabit Ethernet
Ethernet continues
to dominate the Internet. Prices and power
consumption continue to fall, but
performance still goes up. The platform of choice at the high end will
be 10Gbit Ethernet on copper,
while 1Gbit Ethernet will be the bottom end for fabrics. For industrial
use, 100Mbit Ethernet will remain the
mainstay, though 1Gbit Ethernet is pushing its way in. In the mean time, 100Gbit
Ethernet remains on the drawing board—don't expect more than spin this year.
New technology adoption and innovation are more likely to deliver spikes in
price and efficiency with products like Silverback Systems' iSCSI Initiator Host Bus
adapters (). These devices handle
higher-level protocols such as iSCSI and
RDMA, in addition to TCP/IP. Handing off
fabric management to adapters is critical
for minimizing host overhead.
Serial RapidIO
Last
year saw a flood of Serial
RapidIO chips and the initiation of the Serial RapidIO
Interoperability Lab. Excellent interoperability has put
Serial RapidIO in Ethernet's
league.
One key factor behind the
push is the Serial RapidIO
interface's incorporation onto
the processor chip. For example, Freescale's MPC8641D
can be found on Embedded
Planet's EP8641A (). The
AMC-based board has a 4x Serial RapidIO interface that plugs
into a MicroTCA or AdvancedTCA fabric.
Meanwhile, Serial RapidIO is now
being integrated into high-end DSPs,
such as Texas Instruments' C6000 line.
Serial RapidIO provides a way to cluster,
as well as integrate, DSPs into a Serial
RapidIO-based fabric. Overall, Serial
RapidIO is likely to dominate the communications and military arenas for data
plane work.
InfiniBand At The Head Of The
Pack
When it comes to performance
and power, InfiniBand leads the way. It's
the glue that holds together the largest
supercomputers and commercial clusters. This year, it will probably strengthen
its hold—not bad for a technology that
was written off as dead just a couple of
years ago.
Its 4x 20-Gbit/s host interfaces provide
more bandwidth than even a quad-core
processor can use, so there's little chance
this year for movement to the 12x interfaces used on InfiniBand. Still, speed
increases are expected soon, simply to stay
ahead of system requirements.
It's doubtful that InfiniBand will move
onto the processor chip this year,
though the conventional bridge chip
approach should remain. PCI Express to
InfiniBand chips and adapters are available from different sources now. Also,
HyperTransport is becoming more
important to InfiniBand, due to greater
usage of AMD's Opteron in large systems. QLogic's HTX version of its
QLE7140 for PCI Express adapters
allows direct connection
to the Opteron ().
The same protocol stack
is used for both platforms.