Chapter 2. Architecture and technical overview 97
The large cache PCI-X DDR 1.5 GB Cache SAS RAID Adapter (FC 5904) and PCI-X DDR
1.5 GB Cache SAS RAID Adapter (BSC) (FC 5908) uses a SAS Y cable when a single port is
running the EXP12S Expansion Drawer. A SAS X cable is used when a pair of adapters is
used for controller redundancy.
The medium cache PCIe 380 MB Cache Dual - x4 3 Gb SAS RAID Adapter (FC 5903) is
always paired and uses a SAS X cable to attach the feature FC 5886 I/O drawer.
The zero cache PCI-X DDR Dual - x4 SAS Adapter (FC 5912) and PCIe Dual-x4 SAS
Adapter (FC 5901) use a SAS Y cable when a single port is running the EXP12S Expansion
Drawer. A SAS X cable is used for AIX or Linux environments when a pair of adapters is used
for controller redundancy.
The following SAS X cables are available for use with a PCIe2 1.8 GB Cache RAID SAS
adapter (FC 5913):
3 meters (FC 3454)
6 meters (FC 3455)
10 meters (FC 3456)
In each of these configurations, all 12 SAS bays are controlled by a single controller or a
single pair of controllers.
A second EXP12S Expansion Drawer can be attached to another drawer by using two SAS
EE cables, providing 24 SAS bays instead of 12 bays for the same SAS controller port. This
configuration is called cascading. In this configuration, all 24 SAS bays are controlled by a
single controller or a single pair of controllers.
There is a maximum of up to 110 EXP12S Expansion Drawer on SAS PCI controllers.
The FC 5886 drawer can be directly attached to the SAS port on the rear of the Power 770
and 780, providing a low-cost disk storage solution.
Adding the optional 175 MB Cache RAID - Dual IOA Enablement Card (FC 5662) to the
Power 770 and Power 780 causes the pair of embedded controllers in that processor
enclosure to be configured as dual controllers, accessing all six SAS bays. Using the internal
SAS Cable Assembly for SAS Port (FC 1819) connected to the rear port, the pair of
embedded controllers is now running 18 SAS bays (six SFF bays in the system unit and
twelve 3.5-inch bays in the drawer). The disk drawer is attached to the SAS port with a SAS
YI cable. In this 18-bay configuration, all drives must be HDD.
A second unit cannot be cascaded to an EXP12S Expansion Drawer attached in this way.
For details about the SAS cabling, see “Planning for serial-attached SCSI cables” in the
information center:
http://publib.boulder.ibm.com/infocenter/powersys/v3r1m5/index.jsp?topic=/p7had/p7
hadsascabling.htm
2.11.3 EXP24S SFF Gen2-bay drawer
The EXP24S SFF Gen2-bay drawer (FC 5887) is an expansion drawer that supports up to 24
hot-swap 2.5-inch SFF SAS HDDs on POWER6, POWER6+, POWER7, or POWER7+
servers in 2U of 19-inch rack space.
The SFF bays of the EXP24S differ from the SFF bays of the POWER7 or POWER7+ system
units or from the 12X PCIe I/O Drawers (FC 5802 or FC 5803). The EXP24S uses Gen2 or
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