This article (published
here in August, 2001) examines the benefits of applying InfiniBand to create a
centralized server I/O infrastructure, along with the implications of
disaggregating the I/O subsystem from the processor complex.
To
achieve optimal performance in current-generation servers, a dedicated I/O
subsystem, typically based on the PCI local bus, must be tightly bound to each
processing complex. The InfiniBand architecture, which provides an
industry-standard framework for connecting devices via a very low latency, high
bandwidth link, enables the creation of a sharable, centralized I/O
infrastructure. Multiple next-generation servers can be connected to this I/O
infrastructure via InfiniBand links, resulting in many potential benefits,
including data center space savings, bandwidth migration, decreased deployment
cost, simplified systems management, and improved cable management.
Due
to the high cost associated with providing a truly secure and reliable
environment for housing computer equipment, maximizing the utilization of data
center space is becoming increasingly important. Server density has improved
dramatically, and this trend will continue with the introduction of server-blade
technology. Applying InfiniBand to create a sharable, centralized I/O subsystem
will accelerate this trend by allowing designers to replace the dedicated I/O
subsystem associated with each server with InfiniBand connections scaled to meet
the bandwidth and reliability requirements of the server. This will enable
further reductions in the size of each server, resulting in significantly
improved data center space utilization.
In many application
environments, the I/O activity generated by a specific server tends to be
somewhat uneven. Periods requiring high I/O throughput are generally followed by
periods of lower demand. Servers are often configured with sufficient dedicated
capacity to handle the peak bandwidth requirements, but this can result in low
average link utilization. An important benefit of the shared I/O subsystem
approach is that it allows the bandwidth provided by the shared links to migrate
to the servers with the highest demand, providing those servers with
significantly higher instantaneous bandwidth than would be feasible with
dedicated resources, while simultaneously improving link utilization.
In addition to increasing the bandwidth that can be made available to
any given server, the shared I/O model can also significantly reduce the total
cost of deployment with respect to a server cluster. In high-availability
environments, servers often support redundant connections to multiple
infrastructures, including the storage area network, the local area network, and
sometimes a separate inter-process communication network. While effective in
eliminating single points of failure, this can be a costly approach that
requires additional dedicated server ports as well as additional infrastructure
ports. The centralized I/O model allows the I/O bandwidth to be matched to the
requirements of the entire cluster, reducing port count and complexity, with
cost savings of approximately 50 percent.
The reduction in port
connections results in significant business and technical benefits for CIOs and
data center managers as well. Maintaining and growing high-bandwidth data
centers has become increasingly complex and expensive. By deploying a sharable
I/O infrastructure, data center topologies can be simplified, reducing the
amount of equipment to be managed by system administrators. The growing
complexity of the data center cabling matrix can also be substantially reduced.
"Companies have spent thousands of man-hours and millions of
dollars deploying their existing data center networks. Therefore, solutions
involving InfiniBand must be non-disruptive to the current infrastructure, as
well as provide compelling benefits with respect to incumbent technologies,"
explained Philip Murphy, president and co-founder, InfiniCon Systems. "InfiniCon
Systems is focusing its development efforts on these types of solutions."
"Our studies show that a great deal of mindshare has been
generated about InfiniBand. However, system administrators are wary of 'yet
another fabric in the data center,'" notes John Lawler, directing analyst
for E-Business Infrastructure at Infonetics Research. "By positioning its
first generation of products as an extended system backplane and not a new LAN
technology, InfiniCon Systems avoids these potential barriers to adoption."
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