I have a RAID 1 configuration (or will have when I set it up) but I am still concerned about losing important data. So just how safe is RAID1 as a backup strategy? I know it's not a true backup solution since deleting a file off one will be mirrored in the other, but that's not a likely scenario (I only add to my important repositories, never delete from them).
The thing that worries me is that both HDDs will be in the same box in close proximity and therefore prone to the same type of failure at the same time, such as overheating or being subject to a power surge. How likely is this in reality? Am I worrying about nothing? Would you always recommend an offsite backup for critical data as well?
You are right. Many things that can damage the data on one HDD will be accurately duplicated on the other half of the RAID1 array, so proper backups ARE necessary.
I'm using RAID1 as a sort of automatic backup on a particular system. It is the Point-of-Sale system in a family-run retail store. It has no internet connection so risk of external virus attack is low. It runs only the retail software and a clock display utility. The software basically leaves all files closed nearly always. As each transaction occurs it builds a set of data entries in RAM and then, only at the end, opens each necessary file to write new data on the ends, then closes them again.
I bought and installed WinZip Pro. It is programmed to run every night at 11:50 p.m. to make a .zip file copy of ALL the store's data files (they are conveniently stored all together in one subdirectory) and put that file into a different place on the RAID1 array. So now I have an end-of-every-day copy, but still on the same drives. I am depending on the ability to recover at least one of the two zip files for the most recent day if a failure happens. At the end of each month I copy the last day's .zip file off to a USB drive and take it home to a different machine off-site. This is NOT a totally reliable backup system, but not too bad.
We had a motherboard failure recently (Abit). Bought a new mobo (Gigabyte) with all the features we need regarding external connections, etc. Made sure it had nVidia chipset on board, because the original board did. NVidia claimed they always use the same RAID algorithms so any replacement mobo with their chipset RAID built in should work with existing RAID drives. Well, it worked perfectly! Booted the system with new mobo installed and it just ran right away. We ran the new mobo's Driver Install CD to make sure it was all OK with the new devices, then rebooted. Everything just worked with no hiccups, and all the data on those RAID1 drives is there and useable. Yes, we are booting and running from the same drives with no real adjustments at all! We were amazed and relieved it worked.