Not so long ago we had an interesting on site repair. A Dell XPS PC system was refusing to boot properly. After having checked all the obvious stuff we realized that this had a 2Tb RAID (redundant array of independent disks) hard drive array arranged as 2 X 1Tb hard drives. This was where the problem was.
There are seven main varities of RAID, labelled RAID(n) where n is a number between 0-6, with RAID (0) and RAID (1) being the most popular on smaller systems. Each have their own distinct advantages and disavantages.
RAID (0) provides improved performance and additional storage but no fault tolerance. Any drive failure destroys the array, and the likelihood of failure increases with more drives in the array.
RAID (1) allows multiple copies of the same data to be written to more than one physical hard drive, such that if one fails there is less chance of data loss.
One of the hard drives in this particular system had completely failed, to the point where the hard drive was not even spinning up.
We were able to rebuild the machine, with the remaining working hard drive and Windows 7, however it was not possible to recover any of the customer data.
This highlights one of the disadvantages of this particular RAID (0) hard drive system. They will give great performance and data access times providing one of the hard drives does not fail.
If one hard drive does fail as in this case, all of your data is probably NOT going to be recoverable, since a RAID system like this needs a minimum of two drives
RAID (1) would be a better choice as data is written identically to multiple drives, thereby producing a “mirrored set”; at least 2 drives are required to constitute such an array. This allows complete system recovery should one of the hard drives fail.