Raid Solution

We have a 9402-400 with 3 6607 (4GB) disks, currently unprotected. I finally 
got the go-ahead (budget) to implement RAID.
I would just like to ask a few questions to see if I got this right, so here 
goes: 

Because we're at v3r7 the loadsource must be mirrored and the other two disks 
'raided'. Right or wrong?
In order to keep 12GB of diskspace available I need to get three additional 
6607's. Right or wrong?
The way I understand it, my existing three disks are currently connected via 
the MFIOP (rather than a dedicated disk controller) which is a performance 
bottleneck. Right or wrong?
The IBM-reseller is quoting the 6522 raid controller. Are there different (from 
a 
performance point of view) raid controllers I should consider?
Assuming that the new raid controller will connect to all disks, can I expect a 
performance increase regardless of the raid overhead (because the MFIOP is 
out of the picture)?
Does the amount of main storage (ram) used by the system increase with raid? 
Should I look at adding some ram (currently 160MB)?
Maybe I have it all wrong :(

I'd be grateful if someone could put me on the right track.
Thanks,
Matthias

------------------------------------------------------------------------------------------------
Matthias Oertli, Sydney, Australia 

+---
| This is the Midrange System Mailing List!
| To submit a new message, send your mail to "MIDRANGE-L@midrange.com".
| To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---