IBM x3690 X5 Service Manual page 302

You can install a combination of 2.5-inch and 1.8-inch SAS/SATA drive backplanes
in the server for the maximum drive capacity. However, any SAS/SATA adapter
that you install in the server must be capable of supporting two internal, 4-lane
SAS/SATA signal connectors. The following illustrations show the supported
2.5-inch and 1.8-inch SAS/SATA drive backplane configurations and drive IDs
assigned by IMM:
Note: The drive bay IDs can vary, depending on the combination of the
SAS/SATA drive backplanes installed in the server (see "IDs for hot-swap drives"
on page 282 for more information).
The following illustration shows the supported backplane configuration that you
can use to support four drives:
The following illustrations show the supported combination of drive backplane
configurations that you can use to support eight drives:
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System x3690 X5 Types 7147, 7148, 7149, and 7192: Problem Determination and Service Guide
This configuration consists of one 4x2.5-inch drive backplane and requires one
SAS signal cable.
This configuration consists of two 4x2.5-inch drive backplanes and requires two
SAS signal cables.
This configuration consists of one 8x2.5-inch drive backplane and requires two
SAS signal cables.