AIX 5L Problem Determination - IBM Redbooks

Note: This service aid is only present when SSA devices are configured on
the machine.
4.3 Serial Storage Architecture disks
The Serial Storage Architecture (SSA) disk subsystem is capable of being
externally connected to one or more RS/6000 or pSeries systems. Certain
models of RS/6000 and pSeries can also be configured with internal SSA disks.
SSA devices are connected through two or more SSA links to an SSA adapter
that is located in the system used. The devices, SSA links, and SSA adapters are
configured in loops. Each loop provides a data path that starts at one connector
of the SSA adapter and passes through a link (SSA cable) to the devices. The
loop continues through the devices, then returns through another link to a second
connector on the SSA adapter. Each adapter is capable of supporting two loops.
Each loop can have between one and 48 devices. A loop can have as many as
eight SSA adapters connected in up to eight systems, but this is dependent on
the type of SSA adapter being used and how they are configured. Again,
dependent on adapters, disk subsystem, and cables in use, the aggregate loop
speed per adapter can either be 80 MB/s or 160 MB/s. As you can see, the
number of possible combinations is almost endless and changes at each product
announcement. The SSA configuration rules provided in the following section
cover basic considerations.
4.3.1 General SSA setup rules
The following rules must be followed when connecting a 7133 or similar SSA
subsystem:
► Each SSA loop must be connected to a valid pair of connectors on the SSA
adapter card. A1 and A2 form one loop, and B1 and B2 form another loop.
► Only one pair of connectors of an SSA adapter can be connected in a
particular SSA loop. A1 or A2, with B1 or B2, cannot be in the same SSA
loop.
► A maximum of 48 disks can be connected in an SSA loop.
► A maximum of three dummy disk drive modules can be connected next to
each other.
► A maximum of two adapters can be in the same host per SSA loop.
► Cables joining SSA nodes should not exceed 25 meters.
► There is no addressing setup for any SSA device.
► There is no termination since all connections should form a loop.
54 IBM ^ Certification Study Guide - AIX 5L Problem Determination Tools and Techniques