IBM Advanced SerialRAID/X, Руководство по установке

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Appendix A. Connecting SSA Devices to the Adapter
SSA devices can be connected to the adapter and to each other in many ways. Sample
configurations are given in the documentation for the units (for example, the 7133) in
which SSA devices can be installed. Marketing representatives have additional
information on configuring for performance and availability.
The configuration must be planned at the time that the SSA subsystem is ordered. This
must be done so that the correct cables are ordered. This plan should be made
available to whoever installs the adapter and the devices.
This section provides general information on SSA configurations.
SSA Loops and Links
In the simplest SSA configuration, SSA devices are connected through two or more
links to an SSA adapter that is located in a using system. The devices, SSA links, and
SSA adapter are configured in loops. Each loop provides a data path that starts at one
connector of the SSA adapter and passes through a link (SSA cable) to the devices.
The loop continues through the devices, then returns through another link to a second
connector on the SSA adapter.
The maximum permitted length for an external copper cable that connects two SSA
nodes (for example, disk drives) is 25 meters (82 feet).
The maximum permitted length for an external fiber optic cable that connects two SSA
nodes (for example, disk drives) is 10 kilometers (32808 feet).
Details of the rules for configuring SSA loops are given for this SSA adapter in “Rules
for SSA Loops” on page 34.
Loops and Data Paths
All devices that are attached to an SSA adapter,
1
in Figure 2 on page 32, are
connected through SSA links
2
. The SSA links are configured as loops. Data and
commands to a particular device pass through all other devices on the link between the
adapter and the target device.
Data can travel in either direction round a loop. The adapter can, therefore, get access
to the devices
3
(disk drives in this example) through two data paths. The using
system cannot detect which data path is being used.
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