IBM Power 780 Technical Overview And Introduction page 113

The EXP24S SFF Gen2-bay drawer can be ordered in one of three possible mode settings
that are manufacturing-configured (not customer set-up) of 1, 2, or 4 sets of disk bays.
With IBM AIX and Linux the EXP24S can be ordered with four sets of six bays (mode 4), two
sets of 12 bays (mode 2), or one set of 24 bays (mode 1). With IBM i, the EXP24S can be
ordered as one set of 24 bays (mode 1).
There are six SAS connectors on the rear of the EXP24S drawer to which to SAS adapters or
controllers are attached. They are labeled T1, T2, and T3; there are two T1, two T2, and two
T3 connectors. Figure 2-36 shows the rear connectors of the EXP24S drawer.
In mode 1, two or four of the six ports are used. Two T2 ports are used for a single SAS
adapter, and two T2 and two T3 ports are used with a paired set of two adapters or dual
adapters configuration.
In mode 2 or mode 4, four ports are used, two T2 and two T3, to access all SAS bays.
Figure 2-36 EXP24S SFF Gen2-bay drawer rear connectors
An EXP24S drawer in mode 4 can be attached to two or four SAS controllers and provide
much configuration flexibility. An EXP24S in mode 2 has similar flexibility. Up to 24 HDDs can
be supported with any of the supported SAS adapters or controllers.
Include the EXP24S drawer no-charge specify codes with any EXP24S orders to indicate (to
IBM manufacturing) the mode to which to set the drawer. The drawer will be delivered with
this configuration.
Notes:
The modes for the EXP24S drawer are set by IBM manufacturing. There is no option to
reset after the drawer is shipped.
If you order multiple EXP24S drawers, avoid mixing modes within that order. There is
no externally visible indicator regarding the drawer's mode.
Several EXP24S cannot be cascaded on the external SAS connector. Only one
FC 5887 drawer is supported.
The Power 770 or Power 780 supports up to 56 EXP24S SFF drawers.
The EXP24S Drawer rails are a fixed-length and designed to fit Power Systems racks of
28 inches (711 mm) deep. Other racks might have different depths, and these rails will
not adjust. No adjustable depth rails are orderable at this time.
For details about the SAS cabling, see "Planning for serial-attached SCSI cables" in the
information center:
http://pic.dhe.ibm.com/infocenter/powersys/v3r1m5/index.jsp?topic=/p7had/p7hadsasc
abling.htm
Chapter 2. Architecture and technical overview
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