Another Reason to Backup Your RAID Storage

I think most of us feel pretty good about our data that is stored on RAID devices with fault tolerant configurations. Most of my servers are not only fault tolerant but also have hot spares configured. A failed drive will not result in lost data. With RAID 5 or above, it would take at least two failed drives to cause a data loss. I have drives fail occasionally and I replace them as they fail. I have never had two drives fail in the same array simultaneously.

When your disks are configured in a RAID array at fault tolerant levels, failed drives are no longer the biggest risk. A failed RAID controller can cause much more pain. Your drives may be perfectly healthy, but if your controller dies then your data is just as inaccessible as if your disk drives had failed. If you are thinking that replacing that RAID controller is going to solve the problem, then you may be in for a big disappointment. RAID controllers don't encode and store your data in a standard way. You can purchase the latest and greatest RAID controller and plug in your perfectly good drives from your previous array and still have no data.

RAID controllers are not obligated to recognize arrays, logical drives, and data that were created by another RAID controller. The best way to ensure that your data can be recovered is to replace the dead controller with the exact same controller model with the same firmware and revision. This is not always possible because manufacturers update their hardware frequently.

As usual I will end this post by encouraging you to backup your data and keep backup copies offsite. Fault tolerant RAID vastly reduces your chances of losing data due to hard drive failure, but there are other events that can cause your data to be lost. If you value your data enough to store it on fault tolerant systems, then the data is probably valuable enough to backup and store offsite.

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