IBM RS/6000 SP Handbook page 379

2. If the CES system has less than 32 enterprise servers and add SP frames,
leave space for flexible SP node addition.
For example when a CES with 15 enterprise servers is redefined to be
SP-attached servers in the SP system, the servers occupy at least 15 switch
port numbers. If you reserve numbers 0-14 to the enterprise servers, only 15
is left. If in future you want to add an SP node, you can use this number only.
With this switch port number 15, only one thin node is allowed. Therefore, to
provide more flexibility for the addition SP node, it is a good practice to skip
switch port number 12 which can allow a thin node, a wide node, or a high
node to be added to the SP system. One of these nodes is possible to be
hosted in node slot number 13, as shown in Figure 10-19.
To t a l 1 5 s w it c h p o r t n u m b e r s f o r
S P - a tt a c h e d s e r v e r s : 0 -1 1 , 1 3 - 1 5
Figure 10-19 Changing a 15-node CES system to an SP system
The same practice can be applied to a CES with more than 16 and less than 32
nodes. Another example is shown in Figure 10-20 on page 356. To change a
CES to an SP-attached system with 31 enterprise servers, a minimum of two SP
frames are required, since each SP frame can provide up to 16 switch port
numbers only. In this example, you may also skip the switch port number 12 or
28 such that a high, wide or thin node can be added in future.
H ig h / W id e / T h in
n o d e c a n b e a d d e d
h e r e in f u t u r e .
Chapter 10. Clustering configurations
1 2
(s lo t 1 3 )
S P S w itc h
355