"High" cpu usage with ide/sata transfers?

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Today I was rebuilding some raid arrays (delte array, restore from backup) have this setup:

2 x 400GB seagate raid1
2 x 400GB seagate raid1

1 x 250GB ide
1 x 250GB ide

the 250GB ide's are on the motherboard controller (nforce 4 pro)
the 400GB satas are on a promise sata pci-x controller (not pci-e).

task manager is showing roughly 30% of each cpu is eaten constantly during transfers from 1 x 250 -> raid 1 and other 250 -> other raid1

Is this normal?

This is a dual opteron 246 box.
Performon shows total read/write from all logical disks at ~ 190MB/second

Thoughts?