FW V06.XX/HAFM SW V08.02.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DD-TE, July 2004)

Introduction to HP Fibre Channel Products
23SAN High Availability Planning Guide
■ Low latency — The latency is less than 2.5 microseconds between
transmission of a frame at a source port to receipt of the frame at the
corresponding destination port (with no port contention).
■ Local control — Actions taking place at a device N_Port seldom affect
operation of other ports; therefore, servers need to maintain little or no
information about other connected devices in a SAN.
■ Low communication overhead — Fibre Channel protocol provides efficient
use of transmission bandwidth, reduces interlocked handshakes across the
communication interface, and efficiently implements low-level error recovery
mechanisms. This results in little communication overhead in the protocol and
a director bit error rate (BER) less than one bit error per trillion (10
12
) bits.
■ Multiple topology support — Directors support both point-to-point and
multi-switch fabric topologies and indirectly support arbitrated loop topology.
— Point-to-point topology provides a single direct connection between two
device N_Ports. This topology supports bidirectional transmission
between source and destination ports. Through dynamic switching,
directors configure different point-to-point transmission paths. In all
cases, connected N_Ports use 100% of the available bandwidth.
— A multi-switch fabric topology provides the ability to connect directors
and edge switches through expansion ports (E_Ports) and interswitch
links (ISLs) to form a Fibre Channel fabric. Directors receive data from a
device, and based on the destination N_Port address, route the data
through the fabric (and possibly through multiple switch elements) to the
destination device.
— An arbitrated loop topology connects multiple device node loop ports
(NL_Ports) in a loop (or hub) configuration without benefit of a
multi-switch fabric. Although directors do not support direct connection
of arbitrated loop devices, such devices can communicate with directors
through loop switches supplied by HP.
■ Multiple service class support — The Fibre Channel signaling protocol
provides several classes of transmission service that support framing protocol
and flow control between ports. Directors support:
— Class 2 transmission service that provides connectionless multiplexed
frame delivery service with acknowledgment. Class 2 service is best
suited for mainstream computing applications.
— Class 3 transmission service that provides connectionless, best-effort
multiplexed datagram frame delivery with no acknowledgment. Class 3
service is best suited for mass storage or video applications.