Specifications

Chapter 2. Architecture and technical overview 95
2.11.2 EXP24S SFF Gen2-bay Drawer
The EXP24S SFF Gen2-bay Drawer (#5887) is an expansion drawer supporting up to 24
hot-swap 2.5-inch SFF SAS HDDs on POWER6 or POWER7 servers in 2U of 19-inch
rack space.
The SFF bays of the EXP24S are different from the SFF bays of the POWER7 system units
or 12X PCIe I/O Drawers (#5802, #5803). The EXP 24S uses Gen-2 or SFF-2 SAS drives
that physically do not fit in the Gen-1 or SFF-1 bays of the POWER7 system unit or 12X PCIe
I/O Drawers, or vice versa.
The EXP24S SAS ports are attached to SAS controllers, which can be a SAS PCI-X or PCIe
adapter or pair of adapters. The EXP24S SFF Gen2-bay Drawer can also be attached to an
imbedded SAS controller in a server with an imbedded SAS port. Attachment between the
SAS controller and the EXP24S SAS ports is via the appropriate SAS Y or X cables.
The SAS adapters/controllers that support the EXP24S are:
򐂰 PCI-X 1.5 GB Cache SAS RAID Adapter 3 Gb (#5904, #5906, #5908)
򐂰 PCIe 380 MB Cache SAS RAID Adapter 3 Gb (#5805, #5903)
򐂰 PCIe Dual-x4 SAS Adapter 3 Gb (#5901, #5278)
򐂰 PCIe2 1.8GB Cache RAID SAS Adapter (#5913)
The SAS disk drives contained in the EXP24S SFF Gen2-bay Drawer are controlled by one
or two PCIe or PCI-X SAS adapters 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 desired.
Adding the optional 175 MB Cache RAID - Dual IOA Enablement Card (#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 (#1819) connected to the rear port, the pair of embedded
Note: The following consideration should be applied:
򐂰 The large cache PCI-X DDR 1.5 GB Cache SAS RAID Adapter (#5904) and PCI-X
DDR 1.5 GB Cache SAS RAID Adapter (BSC) (#5908) use an SAS Y cable when a
single port is running the EXP24S. 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 (# 5903) is
always paired and uses a SAS X cable to attach the feature #5887 I/O drawer.
򐂰 The zero cache PCI-X DDR Dual - x4 SAS Adapter (#5912) and PCIe Dual-x4 SAS
Adapter (#5901) use a SAS Y cable when a single port is running the EXP24S. A
SAS X cable is used for AIX or Linux environments when a pair of adapters is used for
controller redundancy.
򐂰 The PCIe Gen2 1.8GB Cache RAID SAS Adapter (#5913) uses SAS YO cables.
򐂰 In all of these configurations, all 24 SAS bays are controlled by a single controller or a
single pair of controllers.
򐂰 A second EXP24S drawer can be attached to another drawer by using two SAS EE
cables, providing 48 SAS bays instead of 24 bays for the same SAS controller port. This
configuration is called cascading. In this configuration, all 48 SAS bays are controlled
by a single controller or a single pair of controllers.
򐂰 The EXP24S SFF Gen2-bay Drawer can be directly attached to the SAS port on the
rear of the Power 770 and Power 780, providing a very low-cost disk storage solution.