Hi
First. Don't be frustated.
AIX and VIOS is quite easy. Easier than other UNIXes.
Yes. There's a default LPAR definition that resembles the FullSystem Partition profile of older p6xx Series managed by HMC connected via Serial. This profile reserves all resources of the machine. You can either keep it or not as well as you do't activate it if your server is partitioned. In order to create other LPARs (including those for VIOS LPARs) you need can take a look of the following link:
POWER5 Virtualization: How to set up the SUSE Linux Virtual I/O Server
You don't assign disks to LPARS, you assing adapters, say ethernet, fiber channel, scsi, even serial adapters, and once you have installed the OS (Linux,
AIX, VIOS) you can see the disks connected to those adapters.
The best (IMHO) solution is to create a VIOS LPAR with some features as:
512 MB RAM
0.5 to 1 CPU
At least once SCSI adapter for internal disks where VIOS can be installed and mirrored. Even better, assign an HBA adapter and install VIOS on SAN disks (if available). You can alse use SCSI adapters to connect to SCSI storage boxes as IBM 2104 or IO Expansions as IBM 7133.
At least one HBA to connect to disks on the SAN
At least the IDE adapter for DVD (in desired mode).
can't you start the VIOS LPAR because the default partition what ??? You need to be sure your default LPAR is not activated. Shutdown it down and remeber that when powering on your pSeries select the Partition Standby option so you can control which LPARs starts.
Hope this helps