McDATA StorageWorks 2/140 - Director Switch Planning Manual page 196

Implementing SAN Internetworking Solutions
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McDATA Products in a SAN Environment - Planning Manual
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• Fast Ethernet - A transmission medium specified by IEEE 802.3
that carries information at 100 Mbps (full-duplex) in baseband
form using Category-5 copper cable or fiber-optic cable. The
specification was developed to enable faster communication of
LAN-connected computers. Fast Ethernet is also called 100
Base-T. The iFCP protocol overhead for a fast Ethernet link is
6.3%, which provides a bandwidth of 93.70 Mbps (11.71 MBps)
for storage traffic.
• Optical Container 3 (OC-3) - A specification that defines the
transport level for SONET traffic transmitted at 155.52 Mbps
(full-duplex) using fiber-optic cable.
— The iFCP protocol overhead for a PoS OC-3 link is 8.9%,
which provides a bandwidth of 141.65 Mbps (17.71 MBps) for
storage traffic.
— The iFCP protocol overhead for an ATM OC-3 link is 17.9%,
which provides a bandwidth of 127.74 Mbps (15.97 MBps) for
storage traffic.
• Optical Container 12 (OC-12) - A specification that defines the
transport level for SONET traffic transmitted at 622.08 Mbps
(full-duplex) using fiber-optic cable.
— The iFCP protocol overhead for a PoS OC-12 link is 8.9%,
which provides a bandwidth of 566.59 Mbps (70.82 MBps) for
storage traffic.
— The iFCP protocol overhead for an ATM OC-12 link is 17.9%,
which provides a bandwidth of 510.98 Mbps (63.87 MBps) for
storage traffic.
• Gigabit Ethernet - A transmission medium specified by IEEE
802.3 that carries information at 1,000 Mbps (full-duplex) in
baseband form using Category-5 copper or fiber-optic cable. The
iFCP protocol overhead for a GbE link is 6.3%, which provides a
bandwidth of 937.00 Mbps (117.12 MBps) for storage traffic.
As a practical example, suppose the changes to a one-terabyte
database must be backed up daily on a real-time basis. The changes
constitute 10% of the database per eight-hour working day. Imposing
a 2:1 data compression ratio and performing the computations yields
a backup requirement of 1.74 MBps. An DS3 link (ATM) with a
bandwidth of 4.32 MBps is the appropriate choice. This link provides
nearly 2.5 times the required bandwidth to account for current
storage traffic, unexpected burstiness, and capacity planning.