Thanks guys, how about using RAID 1, but if one of the disk fails, will it still work, or need to replace the damage disk first for it to work?
First rule of backups: RAID is not a backup! Considering any kind of RAID to be a backup is a common misconception.
The primary purpose of most RAIDs (other than 0 which is to increase speed) is to provide redundancy should a data disk go belly up from it's own failure. The RAID will allow a computer to continue to write and read data until the dead disk can be replaced. This is valuable, if not essential, for scenarios where a dead disk would be more than a mere inconvenience, such as in business applications.
The reason RAID is not suitable for backups is malware, mechanical failure in the computer or wherever the RAID is kept (such as blown PSU), natural disaster, or human error will cause all data to be corrupted or lost from the RAID.
Let's say you put drives F and G into RAID 1 in your computer. If your PSU should fail (and they frequently do so quite spectacularly), it could shoot voltage directly from the mains to both of your disks, instantly frying them and, usually, your data. If you drop the computer, there is an excellent chance neither of the HDDs will survive. If you get a virus and it corrupts or deletes the data on your F disk, the data on the G disk will also be corrupted or deleted. If you accidentally delete some data on F, the same data on G also goes away.
This is why it's important to keep your backups separate from your computer. A bare bones backup scheme has at least one backup however, a fire, flood, theft, etc. that damages or destroys your computer could do the same for your data. That is why having two backups, one kept onsite for convenience, and one kept offsite to help protect it from the fate of your computer and onsite backup is highly recommended.
The downside of an offsite backup is the difficulty of keeping it up to date. Data cannot be recovered unless it has been backed up. The easiest and least expensive way to achieve an off site backup and keep it up to date is to use a good paid backup service. I personally use
Carbonite which costs me only $59 a year. It quietly uploads your data to Carbonite's servers, encrypting it before it ever leaves your computer, as soon as it has been created or changed. Carbonite also has a 30 day versioning policy; data is kept for 30 days after it has been changed or deleted, giving you the opportunity to recover the earlier version if needed.
Carbonite has a more expensive plan—$99/year—that both uploads your data to its servers and maintains a mirror on an external HDD. While I discourage using mirrors, in this case, since you could recover your data from Carbonite should both the F and G drive (G being the mirror) fail or become corrupted as long as you discover the problem and freeze the Carbonite backup within 30 days of the failure so you will have time to recover your data. Since you are looking for an automatic solution, this might work for you.
I do not recommend using Carbonite as your sole backup since it takes a long time to upload and download large amounts of data and, though highly unlikely, it is possible even Carbonite could lose your data.
. In my experience there are many ways to mitigate against data loss, and some of them dont require extreme practices at all. A functioning RAID 1.5 or 10, with an option of external storage is as good as a more extreme version. I work with very large and very valuable datasets, but I try to enjoy that without worrying about too much about whether my backup of my backup of my backup is sufficient. There are many ways to skin a cat, but they dont all require precision surgery.
