IBM Power 720 Overview page 109

In addition the EXP24S drawer can also be connected to the integrated SAS controllers in the
EXP30 Ultra SSD I/O drawer. The SAS controller and the EXP24S SAS ports are attached
using the appropriate SAS Y or X or EX cables.
Note: A single FC 5887 drawer can be cabled to the system enclosure external SAS port
when an FC EJ01 DASD backplane is part of the system. A 3 Gbps YI cable (FC 3686,
FC 3687) is used to connect a FC 5887 to the system enclosure external SAS port.
A single FC 5887 is not allowed to attach to the system enclosure external SAS port when
an FC EPCK processor (4-core) is ordered or installed on a single socket Power 720
system.
The SAS disk drives contained in the EXP24S drawer are controlled by one or two PCIe SAS
adapters that are connected to the EXP24S through SAS cables. The SAS cable varies,
depending on the adapter being used, the operating system being used, and the protection
wanted.
In addition to the existing SAS disks options, IBM offers the following disk models:
900 GB 10K RPM SAS HDD in Gen-2 Carrier for AIX and Linux (FC 1752)
856 GB 10K RPM SAS HDD in Gen-2 Carrier for IBM i (FC 1738)
The EXP24S can be ordered in one of three possible manufacturing-configured mode
settings (not customer set-up): 1, 2, or 4 sets of disk bays.
With IBM AIX, and Linux, the EXP24S drawer 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 drawer can be ordered as one set of 24 bays (mode 1).
Notes:
The modes for the EXP24S drawer are set by IBM manufacturing. There is no reset
option 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 drawers cannot be cascaded on the external SAS connector. Only one
FC 5887 is supported.
The Power 720 and Power 740 support up to 14 EXP24S drawers.
There are six SAS connectors on the rear of the EXP24S drawer to which the SAS adapters
or controllers are attached. They are labeled T1, T2, and T3; there are two T1, two T2, and
two T3 (Figure 2-35 on page 96):
In mode 1, two or four of the six ports are used. Two T2 are used for a single SAS
adapter, and two T2 and two T3 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.
Chapter 2. Architecture and technical overview
95