Originally Posted by LMiller7
RAID 1 is of considerable value ... to allow continuous access to your data even in the event of a drive failure. Drive replacement can be deferred to a more convenient time. On a busy network this is of considerable value where taking a server down can be very disruptive to network usage. This is not normally a serious problem on a desktop and the cost of RAID 1 is often difficult to justify.
Unfortunately, many home users see RAID 1 as a form of automatic backup. This is dangerous because it offers protection only from drive failure and none for other causes of data loss. No form of RAID is a replacement for maintaining backups.
I've been running RAID 1 for a few years on my primary desktop to maintain 'continuous access in case of a drive failure' and to 'postpone replacement to a more convenient time'. I have matching drives in other systems on my SOHO network so that in theory a spare is always available. However, in practice, the spares always get used for something which needs to be migrated before they truly become spare. My experience has been that there is never a convenient time for a replacement.
With RAID 1 on my desktop I was doing weekly incremental backups with monthly full backups to a RAID-protected NAS. My present thought is that RAID 1 (or any other level) is not a good match for an OS-drive in a PC where the drive count is minimized to reduce system power. That is why I will be trying hourlies to a second internal drive with dailies to the RAID-protected NAS.
In a previous life as an employee of a major computer manufacturer I designed RAID hardware-firmware-software for Enterprise Systems. Migrating that knowledge into a SOHO system is an ongoing learning experience.