Specifications

80 IBM Power 770 and 780 Technical Overview and Introduction
You can configure the two embedded controllers together as a pair for higher redundancy or
you can configure them separately. If you configure them separately, they can be owned by
different partitions or they could be treated independently within the same partition. If
configured as a pair, they provide controller redundancy and can automatically switch over to
the other controller if one has problems. Also, if configured as a pair, both can be active at the
same time (active/active) assuming that there are two or more arrays configured, providing
additional performance capability as well as redundancy. The pair controls all six small form
factor (SFF) bays and both see all six drives. The dual split (3/3) and triple split (2/2/2)
configurations are not used with the paired controllers. RAID 0 and RAID 10 are supported,
and you can also mirror two sets of controller/drives using the operating system.
Power 770 and Power 780, with more than one CEC enclosure, support enclosures with
different internal storage configurations.
Adding the optional 175 MB Cache RAID - Dual IOA Enablement Card (#5662) causes the
pair of embedded controllers in that CEC drawer to be configured as dual controllers,
accessing all six SAS drive bays. With this feature you can get controller redundancy,
additional RAID protection options, and additional I/O performance. RAID 5 (a minimum of
three drives required) and RAID 6 (a minimum of four drives required) are available when
configured as dual controllers with one set of six bays. Feature #5662 plugs in to the disk or
media backplane and enables a 175 MB write cache on each of the two embedded RAID
adapters by providing two rechargeable batteries with associated charger circuitry.
The write cache can provide additional I/O performance for attached disk or solid-state drives,
particularly for RAID 5 and RAID 6. The write cache contents are mirrored for redundancy
between the two RAID adapters, resulting in an effective write cache size of 175 MB. The
batteries provide power to maintain both copies of write-cache information in the event that
power is lost.
Without feature #5662, each controller can access only two or three SAS drive bays.
Another expansion option is an SAS expansion port (#1819). The SAS expansion port can
add more SAS bays to the six bays in the system unit. A # 5886 EXP 12S SAS disk drawer is
attached using a SAS port on the rear of the processor drawer, and its two SAS bays are run
by the pair of embedded controllers. 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, and the embedded controllers are
connected to the port using a feature #1819 cable assembly. In this 18-bay configuration, all
drives must be HDDs.
IBM i supports configurations using one set of six bays but does not support logically splitting
the backplane into split (dual or triple). Thus, the 175 MB Cache RAID - Dual IOA Enablement
Card (#5662) is required if IBM is to access any of the SAS bays in that CEC enclosure. AIX
and Linux support configurations using two sets of three bays (3/3) or three sets of two bays
Note: These solid-state drives (SSD) or hard disk drive (HDD) configuration rules apply:
򐂰 You can mix SSD and HDD drives when configured as one set of six bays.
򐂰 If you want to have both SSDs and HDDs within a dual split configuration, you must use
the same type of drive within each set of three. You cannot mix SSDs and HDDs within
a subset of three bays.
򐂰 If you want to have both SSDs and HDDs within a triple split configuration, you must
use the same type of drive within each set of two. You cannot mix SSDs and HDDs
within a subset of two bays. The #5901 PCIe SAS adapter that controls the remaining
two bays in a triple split configuration does not support SSDs.