If you did not check the option to automatically rebuild the array, then the only solution I've found to work is to erase the RAID. You will need to backup the data before you do this, then after you erase the RAID you can restore the data from the temporary backup.
By erase the RAID I don't mean break the RAID and erase each drive, then re-configure. Just use Disk Utility to erase the existing RAID mounted on your Desktop.
OK, it looks like when I repaired it or Rebuilt it after it failed it didnt mirror up to the other. Do I need to erase the RAID, then rebuild it? Will that mirror up to the other mirror I have?
Or do I have to erase both RAIDS and start over? I am trying to figure all this RAID and server stuff out so thank you for your help.
I don't know that you can rebuild the data. But as for the RAID itself you need to remove it from Disk Utility, then create a new RAID adding these two drives. The new RAID will be blank.
Now, that said I know that in theory when this problem occurs that if you have one good, populated drive in the RAID but have replaced a bad drive with a new one that the RAID is supposed to "come back." But, I have only tried this once but I probably did not do it correctly because it did not work. I've not seen any discussions about doing this with a working procedure outlined, so I don't want to tell you what I think you should do because it may be wrong.
You can rebuild the mirror.. it should have been done from the RAID set.
Its possible to demote the RAID, the active drive becomes a stand alone drive, then you can create a new RAID set based on that drive and then add the other drive.. must be done from terminal.
If you haven't been down this road before- then may be better to clone to external, remirror the drive pair, then clone from external to raid.