|
Definition
InfiniBand is a powerful
new architecture designed to support I/O connectivity for the Internet infrastructure.InfiniBand
is supported by all the major OEM server vendors as a means to expand beyond and
create the next generation I/O interconnect standard in servers. For the first
time, a high volume, industry standard I/O interconnect extends the role of traditional
"in the box" busses. InfiniBand is unique in providing both, an "in
the box" backplane solution an external interconnect and "Bandwidth
Out of the box", thus it provides connectivity in a way previously reserved
only for traditional networking interconnects. This unification of I/O and system
area networking requires a new architecture that supports the needs of these two
previously separate domains. Underlying
this major I/O transition is InfiniBand's ability to support the Internet's requirement
for RAS: reliability, availability, and serviceability. This white paper discusses
the features and capabilities which demonstrate InfiniBand's superior abilities
to support RAS relative to the legacy PCI bus and other proprietary switch fabric
and I/O solutions. Further, it provides an overview of how the InfiniBand architecture
supports a comprehensive silicon, software, and system solution. The comprehensive
nature of the architecture is illustrated by providing an overview of the major
sections of the InfiniBand 1.0 specification. The scope of the 1.0 specification
ranges from industry standard electrical interfaces and mechanical connectors
to well defined software and management interfaces.
Amdahl's
Law is one of the fundamental principles of computer science and basically states
that efficient systems must provide a balance between CPU performance, memory
bandwidth, and I/O performance. At odds with this, is Moore's Law which has accurately
predicted that semiconductors double their performance roughly every 18 months.
Since I/O interconnects are governed by mechanical and electrical limitations
more severe than the scaling capabilities of semiconductors, these two laws lead
to an eventual imbalance and limit system performance. This would suggest that
I/O interconnects need to radically change every few years in order to maintain
system performance. In fact, there is another practical law which prevents I/O
interconnects from changing frequently - if it am not broke don't fix it.
Bus architectures have a tremendous
amount of inertia because they dictate the bus interface architecture of semiconductor
devices. For this reason, successful bus architectures typically enjoy a dominant
position for ten years or more. The PCI bus was introduced to the standard PC
architecture in the early 90's and has maintained its dominance with only one
major upgrade during that period: from 32 bit/33 MHz to 64bit/66Mhz. The PCI-X
initiative takes this one step further to 133MHz and seemingly should provide
the PCI architecture with a few more years of life. But there is a divergence
between what personal computer and servers require.
Personal
Computers or PCs are not pushing the bandwidth capabilities of PCI 64/66. PCI
slots offer a great way for home or business users to purchase networking, video
decode, advanced sounds, or other cards and upgrade the capabilities of their
PC. On the other hand, servers today often include clustering, networking (Gigabit
Ethernet) and storage (Fibre Channel) cards in a single system and these push
the 1GB bandwidth limit of PCI-X.
<<back |