It would be very nice to hear more about the software and hardware of your config.
1.5 hrs to re-build RAID1 on a 2/3 full pair of 500 GB drives is a nice performance - I am currently using a NSLU2 device and when I changed the backup drive, it took over 56 hours
to do a disk 1 to disk 2 backup of about 568 GB.
(This is a 2004 era gadget that has 2 USB ports and 1 ethernet ports, it shares the contents of the USB drives over ethernet and can be configed - as I have done - where one drive gets a daily backup from the other, a cheap approximation to a true RAID1 system)
The performance of this thing sucks and I need to figure something new.http://en.wikipedia.org/wiki/NSLU2
Any help you can offer is appreciated