Cisco Cisco MDS 9000 XRC Acceleration White Paper
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Figure 1. Relationship Between Data Center Distances and Application Availability
Technology plays a critical role in determining how, when, and where the business recovery starts after an outage. This technology includes the
protection or duplication of the physical IT infrastructure, a one-time operation and replication of the data from the primary site to the secondary
site, and ongoing daily operations. Applications platforms, including their supporting hardware and software, can be protected by the following
technologies:
protection or duplication of the physical IT infrastructure, a one-time operation and replication of the data from the primary site to the secondary
site, and ongoing daily operations. Applications platforms, including their supporting hardware and software, can be protected by the following
technologies:
Data center clusters for application availability within a given data center
Metro or geo clusters for metropolitan distances, to keep the applications continuously available
Standby platforms and applications to help restore business operations in time to meet business objectives
Figure 1 shows the relationship of application-platform availability and distance between data centers.
Data replication is a complex task and the method of replication is determined by the criticality of the application using the data. For mission-
critical applications it is mandatory that no data be lost and that downtime is kept to an absolute minimum, whereas other applications can
withstand significantly longer interruptions. Data-replication technologies that are available are; include coarse wavelength-division multiplexing
(CWDM), dense wavelength-division multiplexing (DWDM), and Fibre Channel over IP (FCIP). CWDM combines up to 16 wavelengths onto a
single fiber. CWDM technology uses an ITU-standard 20-nanometer (nm) spacing between the wavelengths, from 1310 nm to 1610 nm. This
technology does not amplify or regenerate the light signals, or in other words is passive repeater, and therefore is limited to shorter distances of
up to 80 km.
withstand significantly longer interruptions. Data-replication technologies that are available are; include coarse wavelength-division multiplexing
(CWDM), dense wavelength-division multiplexing (DWDM), and Fibre Channel over IP (FCIP). CWDM combines up to 16 wavelengths onto a
single fiber. CWDM technology uses an ITU-standard 20-nanometer (nm) spacing between the wavelengths, from 1310 nm to 1610 nm. This
technology does not amplify or regenerate the light signals, or in other words is passive repeater, and therefore is limited to shorter distances of
up to 80 km.
DWDM combines up to 64 wavelengths onto a single fiber. DWDM technology uses an ITU-standard 100-GHz or 200-GHz spacing between the
wavelengths, arranged in several bands at ~1500 to 1600 nm. In this technology the wavelengths are closer together with respect to CWDM, and
therefore more accurate. The advantage is a much higher density of wavelengths, and the fact that the light signals can be amplified and
regenerated allows for longer distances, with regeneration for approximately every 150 km.
therefore more accurate. The advantage is a much higher density of wavelengths, and the fact that the light signals can be amplified and
regenerated allows for longer distances, with regeneration for approximately every 150 km.
The data transport medium in wavelength division multiplexing is an optical fiber cable, often referred to as “dark fiber.”