The HP Extended Cluster for RAC architecture relies on the same components as the collocated system configuration, but it introduces several additional key technologies.
Figure 2. DWDM: Dense Wavelength Division Multiplexing
DWDM employs optoelectronic technology to simultaneously transmit multiple separate optical signals through a single optical fiber by changing the wavelength of the incoming optical signals to permit coexistence on a common fiber2.
The transmitting DWDM device can multiplex multiple converted optical inputs over the same fiber optic cable. The destination DWDM reverses the process; it demultiplexes the signals and converts them back to their original wavelength. This process allows network, disk, and application communications to share the same DWDM link and provides the capability to extend the Fibre Channel link distances. Examples shown in Figure 2 include the multiplexing and demultiplexing of Fibre Channel,
The DWDMs and fiber optic media together provide the low latency interconnect that is essential to RAC performance and scalability.
Dark fiber is existing fiber optic cable that has not yet been lit. This excess fiber capacity is readily available, and using it to connect DWDM devices is rapidly gaining popularity as a
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