User guide

40 Implementing Cisco InfiniBand on IBM BladeCenter
3.5.1 Application clustering
The Internet today has evolved into a global infrastructure supporting applications such as
streaming media, business-to-business solutions, e-commerce, and interactive portal sites.
Each of these applications must support an ever-increasing volume of data and demand for
reliability. Service providers are in turn experiencing tremendous pressure to support these
applications. They must route traffic efficiently through increasingly congested
communication lines while offering the opportunity to charge for differing QoS and security
levels. Application Service Providers (ASP) have arisen to support the outsourcing of
e-commerce, e-marketing, and other e-business activities to companies specializing in
Web-based applications.
These ASPs must be able to offer highly reliable services that offer the ability to dramatically
scale in a short period of time to accommodate the explosive growth of the Internet. The
cluster has evolved as the preferred mechanism to support these requirements. A cluster is
simply a group of servers connected by load-balancing switches working in parallel to serve a
particular application.
InfiniBand simplifies application cluster connections by unifying the network interconnect with
a feature-rich managed architecture. InfiniBand’s switched architecture provides native
cluster connectivity, thus supporting scalability and reliability inside and out of the box.
Devices can be added and multiple paths can be utilized with the addition of switches to the
fabric. High-priority transactions between devices can be processed ahead of lower-priority
items through QoS mechanisms built into InfiniBand.
3.5.2 Interprocessor communication
Interprocessor communication enables multiple servers to work together on a single
application. A high-bandwidth, low-latency reliable connection is required between servers to
ensure reliable processing. Scalability is critical as applications require more processor
bandwidth. The switched nature of InfiniBand provides connection reliability for
interprocessor communication systems by allowing multiple paths between systems.
Scalability is supported with fully hot-swappable connections managed by a single unit
(subnet manager). With multicast support, single transactions can be made to multiple
destinations. This includes sending to all systems on the subnet, or to only a subset of these
systems. The higher-bandwidth connections (4X, 12X) defined by InfiniBand provide
backbone capabilities for interprocessor communication clusters without the need for a
secondary I/O interconnect.
3.5.3 Storage area networks
Storage area networks are groups of complex storage systems connected through managed
switches to allow very large amounts of data to be accessed from multiple servers. Today,
storage area networks are built using Fibre Channel switches, hubs, and servers that are
attached through Fibre Channel host bus adapters (HBA). Storage area networks are used to
provide reliable connections to large databases of information that the Internet Data Center
requires. A storage area network can restrict the data that individual servers can access,
thereby providing an important partitioning mechanism (sometimes called zoning or fencing).
The fabric topology of InfiniBand enables communication between storage and server to be
simplified. Removal of the Fibre Channel network enables servers to directly connect to a
storage area network without a costly HBA. With features such as Remote DMA (RDMA)
support, simultaneous peer-to-peer communication, and end-to-end flow control, InfiniBand
overcomes the deficiencies of Fibre Channel without the need for an expensive, complex
HBA.