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216 IBM System Storage DS6000 Series: Copy Services with IBM System z
18.7.2 Logical paths
We recommend that you read the discussion presented in 13.4.2, “Logical paths” on
page 144, in the Metro Mirror chapter, because it is also valid for Global Copy.
18.8 Distance considerations
The maximum distance for a direct Fibre Channel connection is 10 km. If you want to use
Global Copy over longer distances, the following connectivity technologies can be used to
extend this distance:
Fibre Channel switches
Channel Extenders over Wide Area Network (WAN) lines
Dense Wave Division Multiplexors (DWDM) on dark fibre
Channel extender
Channel extender vendors connect DS6000 systems with a variety of Wide Area Network
(WAN) connections, including Fibre Channel, Ethernet/IP, ATM-OC3, and T1/T3.
When you use channel extender products with Global Copy, the channel extender vendor
determines the maximum distance supported between the primary and secondary DS6000.
Contact the channel extender vendor for their distance capability, line quality requirements,
and WAN attachment capabilities.
A complete and current list of Global Copy supported environments, configurations, networks,
and products is available in the DS6000 Interoperability Matrix.
Consult the channel extender vendor about hardware and software prerequisites if you are
using their products in a DS6000 Global Copy configuration. Evaluation, qualification,
approval, and support of Global Copy configurations using channel extender products is the
sole responsibility of the channel extender vendor.
Dense Wave Division Multiplexor (DWDM)
Wave Division Multiplexing (WDM) and Dense Wave Division Multiplexing (DWDM) comprise
the basic technology of fibre optical networking. The technique is used to carry many
separate and independent optical channels on a single dark fibre.
A simple way to envision DWDM is to consider that, at the primary end, multiple fibre optic
input channels (such as ESCON, Fibre Channel, FICON, or Gbit Ethernet) are combined by
the DWDM into a single fibre optic cable. Each channel is encoded as light for a different
wavelength. Think of each individual channel as an individual color: the DWDM system is
transmitting a rainbow.
At the receiving end, the DWDM fans out the different optical channels. DWDM, by the very
nature of its operation, provides the full bandwidth capability of the individual channel. As the
wavelength of light is, from a practical perspective, infinitely divisible, DWDM technology is
only limited by the sensitivity of its receptors, as the total aggregate bandwidth possible.
A complete and current list of Global Copy supported environments, configurations, networks,
and products is available in the DS6000 Interoperability Matrix.
Contact the DWDM vendor regarding hardware and software prerequisites when using their
products in an DS6000 Global Copy configuration.