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Fibre to SAS/SATA RAID Subsystem
User Manual 19
1.3.3 Basic Elements
The following elements are the connectivity of storages and Server components using
the Fibre channel technology.
Cables and connectors
There are different types of cables of varies lengths for use in a Fibre Channel
configuration. Two types of cables are supported: Copper and Optical (fiber).
Copper cables are used for short distances and transfer data up to 30 meters per link.
Fiber cables come in two distinct types: Multi-Mode fiber (MMF) for short
distances (up to 2km), and Single-Mode Fiber (SMF) for longer distances (up to
10 kilometers). B y d e f a u l t , t h e R A I D s u b s y s t e m supports two short-wave
multi-mode fibre optic SFP connectors.
Fibre Channel Adapter
Fibre Channel Adapter is a device that is connected to a workstation, server, or host
system and control the protocol for communications.
Hubs
Fibre Channel hubs are used to connect up to 126 nodes into a logical loop. All
connected nodes share the bandwidth of this one logical loop. Each port on a hub
contains a Port Bypass Circuit(PBC) to automatically open and close the loop to
support hot pluggability.
Switched Fabric
Switched fabric is the highest performing device available for interconnecting large
number of devices, increasing bandwidth, reducing congestion and providing
aggregate throughput.
Each device is connected to a port on the switch, enabling an on-demand connection
to every connected device. Each node on a Switched fabric uses an aggregate
throughput data path to send or receive data.
1.3.4 LUN Masking
LUN masking is a RAID system-centric enforced method of masking multiple LUNs
behind a single port. By using World Wide Port Names (WWPNs) of server HBAs,
LUN masking is configured at the volume level. LUN masking also allows s h a r i n g
disk storage resource across multiple independent servers. A single large RAID
device can be sub-divided to serve a number of different hosts that are attached to
the RAID through the SAN fabric with LUN masking. So that only one or a limited
number of servers can see that LUN, each LUN inside the RAID device can be limited.
LUN masking can be done either at the RAID device (behind the RAID port) or at the
server HBA. It is more secure to mask LUNs at the RAID device, but not all RAID
devices have LUN masking capability. Therefore, in order to mask LUNs, some HBA
vendors allow persistent binding at the driver-level.