one key point to raid systems is testing that it does actually do what you expect it to do. Before it becomes critical and you are surprised it does not do something you expected it should.

Once the system is set to use raid, test the raid will work as expected, even booting from a degraded raid array, unless you are familiar with repair techniques of raid arrays from a livecd. I however prefer it just boot up and I tell it to use another drive after it boots.

Some tools do not set up a software raid 1 to be able to boot from either drive, as only one partition is marked as boot and/or has grub/lilo installed to one of the drives boot sector. There are some fairly simple commands to ensure that this happens as expected. I'm not really sure why it's not done automatically more often.

When I last installed ubuntu server 10.10 it put grub on both boot sectors but forgot to mark the 2nd drive's partition with a bootable flag, which every partitioning tool can toggle.