RAID 0+1 using 10000rpm and 7200rpm HDD?

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Hello,

I have four (4) HDD in my box :

RAID 0 (on Intel IHC5-R)
Western Digital Raptor 74GB 10000rpm SATA
Western Digital Raptor 74GB 10000rpm SATA

RAID 0 (on Promise FastTrak 378)
Seagate Barracuda 7200.7 120GB 7200rpm SATA
Seagate Barracuda 7200.7 120GB 7200rpm SATA

I would like to create a RAID 0+1 from this config but I wonder if I'm
about to loose on performances doing the RAID 1 between the two (2) RAID 0
volumes since the first volume has 10000rpm HDD and the second one has
7200rpm HDD.

What do you think?

Also note that I will be using linux raid (BIOS RAID is disabled for both
chips) on this Asus P4C800-E Deluxe motherboard.

Many thanks for your time and help.