AIX/ORACLE - Raid devices + async I/O

We are using AIX 3.2.5 and Oracle 7.0.16 and are currently looking at the I/O configuration. Couple of quick questions.

1. The Unix Gang wants to take our raid subsystem and create one filesystem across all five drives in the array replacing the 5 filesystems we have now. The only thing on this array is oracle datafiles so it sounds like a reasonable plan. Instead of having 5 FS's that are striped across 5 disks we'll have 1 FS across the same disks.

   All things being equal, can anybody think of a good reason not to do    this?

2) The Oracle instalation manual make a big todo about the async_io kernel

   extentions. And setting the Oracle initializaion parameter to make use    of async_io does seem to produce a real performance benefit. This was    suprising to me since we are not using raw devices and I would have    expected the FS code to already be asynchronous.

   Are not writes to the JFS already async and if so how does the async_io    option increase performance of I/O?

-- 
Regards, 

Lee E. Parsons                  		
Systems Oracle DBA	 			lparsons_at_world.std.com