"WARNING: aiowait timed out 1 times" message and slow DB.What check

Hi to all,
I'm experiencing a very slow import (24hours for about 45G) in a brand new cluster (sun-cluster 3, Solaris 8), 2 Sun-Fire-480R with 2CPU 900Mz. We have all datafiles on a raid 0+1 Veritas filesystem made over 8 disks (4+4) seagate 36G 10000rpm.
The main wait events are (from V$System_Event)

Wait Event Waits Timeouts Time Waited Average Wait rdbms ipc message 2144871 925069 246679614 115 PX Idle Wait 396350 396354 79335267 200
db file parallel write 15563 0 48594570 3122 pmon timer 149757 134639 39659564 265
smon timer 1940 1266 37142397 19146
SQL*Net mesg from cli 1799654 0 7562073 4 log buffer space 85072 55741 6774074 80
direct path write 53854 0 3698614 69
log file swtch (ckp inc.)34631 34378 3469422 100

I've read the notes abou the WARNING regarding the asyncronous io and I'm afraid that something is configured in a not good way; what should the sysadmin investigate ad the OS level to confirm that? What type of checks we can do?
The import parameter are:
buffer=400000000 feedback=2000 commit=N
I've set the sort_area_size to 128M, the TEMP is locally managed and we are using the UNDOTBS feature,the sga is 2653131224 with 384M of shared_pool. The only process running is the import.
Thanks to all,
Francesco Received on Wed Feb 19 2003 - 02:30:35 CST