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5
Cable and Configuration Guidelines
5-21
Storage System Hardware
Cable and Configuration Guidelines
We recommend that all copper-interconnected nodes be connected to
a common ground grid. The common grid is not needed for optical
interconnections.
Copper cable allows up to 30 meters (99 feet) between nodes or
switches and hubs. Optical cable allows significantly longer
distances. This is a major advantage of optical cable. However, you
can use optical cable from a server only if the server’s adapter
supports optical cable; otherwise you must use copper. Not all
adapters support optical cable.
To connect a DPE to a DAE, you must use copper cable, whose
maximum length is 10 meters (33 ft). So, the distance between a DPE
and the DAEs it controls cannot exceed 10 meters (33 ft).
The host-bus adapters and SPs used with shared storage systems
require optical cable, as does the switch between adapters and SPs.
The SPs used with unshared storage systems support copper cables
and — with MIAs — optical cables. A hub itself supports copper, or
with a MIA, optical. So you can use a copper cable or — with two
MIAs per cable — optical cable between any hub and SP. For optical
cable to work between an adapter and hub or SP, then the adapter
must support optical cable.
Figure 5-10 Comparison Between Optical and Copper Cabling
Server
Server
Maximum distance:
Copper cable: 30 m
Adapter
Switch or hub
Storage system
Adapter
Storage system
Maximum distance:
Copper cable: 30 m
Optical cable:500 m
or more