Introduction to RAID 10 Arrays

RAID 10 Defined

This array level uses at least four hard disks and additional disks must be added in even numbers. The data is first placed into mirrored pairs at the lower level. Next, the controller selects a member from each mirrored pair raid controller and stripes the data into a new logical volume.

Advantages and DisadvantagesThis level of RAID offers several advantages. The most important of these is the fact that it is more fault tolerant than other levels of RAID because of the mirroring of data at the lower level. The array can sustain multiple disk failures as long as an entire mirror is not lost. Another advantage is speed that is obtained when striping at the upper level. The disadvantages of this level are its complexity and reduced capacity. For example, if you have four 500GB disks in a RAID 0 array, the total capacity would be 2TB. In a RAID 10, the total capacity would be 50% or 1TB.

Devices Utilizing RAID 10

There are many devices on the market today that utilize this array level including NAS, SAN, external hard drives, and many servers. Most current RAID controllers commonly offer this level of RAID and many others.

Problems That Can Occur

Although this array level is more fault tolerant than other levels, problems can occur with the hard disks or controller that can cause RAID failure. The data can become lost due to a degraded RAID, rebuild failure, RAID controller failure, power failure, damage to the array configuration, hardware or software problems, array volumes that will not mount and more.

How To Proceed With a Failed RAID

If you are experiencing RAID failure, it is important that the array remain intact. Continuing to use an array in a problematic condition is a recipe for disaster. The very first thing you should do is power off the RAID server immediately to ensure no additional writes are performed to the disks. Any events describing what may have happened to cause the problem should be noted. If the member disk drives are removed from the server, they should be labeled in the correct order they were removed. To ensure a successful recovery of data, it is important that the failed RAID 10 remain intact.

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