Infiniband Frequent Questions - Q& A

2012-12-11 11:38:12

Q: Is InfiniBand designed strictly as an I/O fabric?
A: No, InfiniBand offers much more. At the lowest layer, InfiniBand provides a high performance, low latency, reliable switch fabric to serve as a scalable I/O interconnect. However, InfiniBand offers higher layers of functionality that enable applications such as application clustering, fast IPC (Inter Process Communication), and SANs (Storage Area Networks).

Q: What makes an InfiniBand I/O fabric?
A: An InfiniBand fabric is built up from HCAs, TCAs, and Switches. An HCA is a Host Channel Adapter which provides the mechanism to connect InfiniBand devices to pro-cessors and memory. In addition, an HCA provides a common set of required features to which software may interface through a defined “verb” layer. A TCA is a Target Channel Adapter and is an endpoint of an InfiniBand fabric. The TCA typically pro-vides additional I/O functionality. A switch is used to connect several InfiniBand chan-nel adapters (HCA or TCA), and also to switch devices together, sometimes redundantly. Switch is the mechanism used to create an InfiniBand fabric.

Q: Does InfiniBand support RAS?
A: Yes. RAS stands for Reliability, Availability, and Serviceability. InfiniBand supports reliability with guaranteed reliable services which deliver in-order packet with multiple CRC’s (Cyclical Redundancy Checks) to detect errors. InfiniBand supports availability as it enables redundancy and supports failover by switching to an alternative path, should a link or device fail. Infini- Band supports serviceability through hot swappability and special management functions, which can be either in-band and out-of-band.

Q: What basic bandwidths are supported by InfiniBand?
A: InfiniBand supports three links (1X, 4X, and 12X) which are multiples of the basic 2.5Gb/s rate. Thus, the rates supported are 2.5Gb/s, 10Gb/s, and 30Gb/s. InfiniBand is actually a full duplex bidirectional.