Converting RAID 0 array to RAID 0+1 - Advice sought.

Hi.
I've just built a new machine and have created a stripe set therein
using a Promise FastTrak 100 TX2 controller and 2 Western Digital
WD800JB hard Drives.

Now, I opted to use the PCI IDE controller as I thought It may be
slightly safer than the onboard one inasmuch as I could always move it
and the drives 'as is' to another machine if anything went wrong with
any of the other components.

Am I right in this assumption or should I have used the onboard
controller? Will the PCI bus' bandwdth limitations have an adverse
affect on speeds or is this negligible? My system specs are included
at the bottom of this post.

Anyway, i'm digressing a little here as the main pont of this post is
to determine how I go about converting this 2 drive RAID 0 array into
a 4 drive RAID 0+1 setup as soon as I get another 2 drives. Can this
be done non-destructively?
i.e Will I be able to merely connect each of the two drives as a slave
on each channel and simply enter the FastBuild utility and rebuild the
array so that the existing setup is just mirrored onto the two new
drives?

It would save me a lot of trouble if i can do it this way as the
current stripe set holds my OS etc.
Anyway, thanks in advance for any advice you may have to offer.
Cheers.
Mod.



=========================== SYSTEM SPECS
==================================================

Intel Pentium 4 3.0GHz (800FSB) with HT Technology - Retail x 1

Asus P4C800-E Deluxe "Canterwood" (Socket 478) Motherboard x 1

Corsair 1GB DDR XMS3200C2PT TwinX (2x512MB) CAS2 x 1

Samsung SW-252B 52x/52x/24x CD-ReWriter (Black) - OEM x 1

Samsung SD-616QBB 16x48x DVD-ROM (Black) - OEM x 1

Sapphire ATI Radeon 9600 Pro 128MB DDR TV-Out/DVI - Retail x 1

Akasa Paxmate Acoustic Absorption Mat x 1


Antec TruePower 550W PSU x 1

Western Digital Caviar 80GB Special Edition 8MB Cache - OEM x 2

Lian Li PC 71 Aluminium Full-Tower x 1

Promise Fast FastTrak100 TX2 IDE RAID card.

ThermalRight SLK-947U (Socket 478 & Socket A) Cooler

Hitachi CML174SXWB 17" TFT Monitor (Carbon)

PS, I'd previously posted this message to
alt.comp.periphs.mainboard.asus with no response so please forgive any
duplication if you've already read it there.