Originally posted by RGlasel It is a very poor backup system because if the RAID controller fails you can lose everything and corrupt files are replicated across the array. Please take stevebrot's advice of using external HD's for backup.
Yep! RAID is not backup. As generally used, it provides redundancy and perhaps additional read/write efficiency and nothing more. While some form of RAID is generally "best practice" for critical data storage, so is regular backup to allow a return to a particular point in recent history. Vulnerability to data loss is present at several levels:
- Hard drive media failure (most common and what we fear the most)
- Drive controller failure (less common, but still a risk...results in wholesale disc corruption)
- Destruction/lock by malware
- Accidental deletion (Oops!)
- Intentional deletion (What you mean, "We need that file"?)
- Intentional, but ill-conceived, modification
- Theft (yes, sometimes laptops grow legs)
- Etc...
Of the above, mirroring using RAID only addresses the first point and does a pretty decent job of it. The main advantage is that it is done in real time and recovery is automatic and simple. There are some backup strategies, many of which are cloud-based, that also replicate file system changes in real time, but I am a little wary of solutions that work the hardware double hard in the background while I have real foreground work to get done.
Periodic backup, OTOH, allows at least partial recovery from all of the points in the list and usually to a particular point in time, within the last couple of weeks, depending on the frequency of and nature of the backup. It is generally scheduled to be done at night or some other time of low activity to avoid interruption or degradation of system performance. (A glance at the performance monitors while doing backup operations can be rather enlightening...whole lot of busy going on...)
A professional system admin will configure a data-critical server with disc redundancy (RAID) and separate tape backup done at least daily with the tapes rotated out to secure off-site storage at interval. If I were doing my photography on a professional basis, I would do something similar. The cool thing about cloud storage is that all of those "best practice" protocols are done for you. The bad thing is that your data safety and security is only as good as the service you work with.
Steve