User`s guide

270 Implementing an Open IBM SAN
3.7 ESS configuration guidelines
In this chapter we have addressed some of more commonly encountered
features of the INRANGE director.
The 2042-001 is designed to provide maximum bandwidth switching from any
port in the system to any other port in the system. There is no mandatory
requirement for attachment of server or device ports to the 2042-001.
There are, however, a few guidelines to system configuration that should be
followed to assure optimum system reliability, availability and serviceability of the
overall SAN environment to which the 2042-001 is installed.
The foremost consideration is to spread critical resources across multiple
Director FRUs. The 2042-001 FRU in this instance is the eight port FI/O module.
Device ports should be distributed over as many director FI/Os as available.
Assignment of device ports to the FI/O is not critical and assignment to the same
port number across adjacent FI/Os for convenience is acceptable. When device
ports are allocated to the director, allocation of additional ports in the same
horizontal row should be considered for future expansion.
Channels from a common server or host image should be allocated over multiple
FI/Os in a manner similar to the way device ports are distributed over multiple
FI/Os as described above. In addition, when a server channel is daisy chained to
multiple devices by IOCP, the channel and device ports may be grouped on an
FI/O.
Critical system resources, such as SYSRES storage, may be assigned as device
and channel pairs to take advantage of port pairs on a FI/O that offer the greatest
autonomy of routing. These port pairs are ports 1&2, 3&4, 5&6, 7&8 on every
FI/O. Selection of these ports offers the highest availability in the most adverse
conditions.