By NOT using RAID-1, you will be copying files over to the drive all at once in huge chunks for a long period of time. This stresses the drive more than anything.
When you use RAID-1, read/write happens simultaneously on both drives.
If you want performance and relability, create a RAID 0+1 array. You will require 4 drives and something like the Promise FastTrak TX4000 SATA 3.0gb/s RAID PCI Card.
I run a RAID 0+1 array here on my slackware linux box with a journalling filesystem called REISERFS. Performance over my 100mbps network to my workstation running a RAID 0 array (Two SATA 3gb/s drives connected to Promise TX2300 PCI Card) is 10,000kb/s to 12,000kb/s.
(I'm waiting a few more weeks before I buy my 1gbps network gear, then it should be around 80,000kb/s to 90,000kb/s)