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Storage Architectures and Devices 125
4.8.2.1 PCI SSA Multi-Initiator/RAID EL Adapter
The PCI SSA Multi-Initiator/RAID EL Adapter (# 6215) can be configured as
either a two-initiator non-RAID, or one-initiator RAID adapter. It also has been
enabled to support an optional 4 MB Fast-Write Cache card that improves
write performance in both RAID 5 or non-RAID (one-initiator configurations)
operations. The PCI SSA Multi-Initiator/RAID EL Adapter has four ports, two
SSA loops, and a supported configuration of 48 SSA disk drives per loop, or
96 SSA disk drives. The adapter supports target mode operations and
HACMP.
The PCI SSA Multi-Initiator/RAID EL Adapter, when operated in a RAID 5
configuration, will support (2+P) to (32+P) arrays and up to six (15+P) arrays.
The adapter also supports Hot Spares in RAID 5 mode. All models of the
7133 are supported, as well as the 7131-405 and internal RS/6000 SSA disk
drive configurations. The SSA Fiber optic Extender is also supported. It
requires one PCI adapter slot. Only AIX 4.2.1 and later version of AIX support
this adapter.
The SSA Fast-Write Cache Option Card (# 6222) is a 4 MB fast-write optional
feature that will plug into either SSA Multi-Initiator/RAID EL Adapter. It utilizes
non-volatile RAM and has a data memory retention of over seven years.
During the unlikely event of an SSA Multi-Initiator/RAID EL Adapter failure, a
new SSA Multi-Initiator/RAID EL Adapter can be installed and the SSA
Fast-Write Cache Option Card can be removed from the failing adapter and
installed in the new SSA Multi-Initiator/RAID EL Adapter insuring data
integrity and continuous operation.
The SSA Fast-Write Cache Option Card (# 6222) can provide as much as
10-times improvement of data throughput and response time during certain
sequence write operations compared to SSA RAID adapters without the SSA
Fast-Write Cache. The response time and data transfer improvement using
the option card (# 6222) will vary depending upon the data block sizes, the
percentage of sequential writes, machine type/model, and application
parameters.
The SSA Fast-Write Cache Option Card (# 6222) plugged into SSA
Multi-Initiator/RAID EL Adapter (# 6215) will operate in either non-RAID or
RAID 5 mode, in a one-initiator configuration.
4.8.2.2 SSA Device Drivers
Two types of device drivers provide support for all SSA subsystems:
• The SSA adapter device driver, which deals with the SSA adapter.