Note: In the SSAservice aids, this adapter is called “IBM SSA160 SerialRAIDAdapter
(14109100)”.
The adapter card has four SSAconnectors that are arranged in two pairs. Connectors
A1 andA2 are one pair; connectors B1 and B2 are the other pair.
The SSAlinks must be configured as loops. Each loop is connected to a pair of
connectors at the SSAadapter card. These connectors must be a valid pair (that is, A1
andA2 or B1 and B2); otherwise, the disk drives on the loop are not fully configured,
and the diagnostics fail. Operations to all the disk drives on a particular loop can
continue if that loop breaks at any one point.
This adapter also contains array management software that provides RAID functions to
control the arrays of the RAID subsystem (see also Chapter3, “RAID Functions and
Array States”on page29). An array can contain several member disk drives. Each
array is handled as one disk by the operating system. The array management software
translates requests to this disk into requests to the member disk drives.Although this
adapter is a RAID adapter,it can be configured so that all, some, or none of the disk
drives that are attached to it are member disk drives of arrays.
TheAdvanced SerialRAID Adapter can be connected, by way of one or two SSA loops,
to other SSAadapters. These adapters can be either in the same using system, or in
separate using systems. (See “Rules for SSALoops”on page 22 for details of valid
configurations.)
Fast-Write Cache Feature
An optional 32 MB Fast-Write Cache feature is available for theAdvanced SerialRAID
Adapter.This feature improves performance for jobs that include many write operations.
128 MB Memory Module Feature
An optional 128 MB dual inline memory module (DIMM) feature is available. This
feature is recommended for two-way fast-write operations.
Chapter1. IntroducingSSA and the Advanced SerialRAIDAdapters 5