Charles assessed the recovered data and tested the client’s critical Quickbooks files and Taxwise documents for any signs of corruption. Since there had been sectors on the two failed drives we couldn’t read, there was a possibility that some of the data was corrupted. The client’s most critical data, though, was intact. Upon request, we sent the client a list of all of the files we had recovered. The client was pleased with the result and paid the bill for our Dell server recovery services. We sent their data back to them on a healthy, new hard drive. Our engineers ranked this Dell server recovery case a 9 on our ten-point scale.
While the client did have a hot spare, it wasn’t able to protect their RAID-5 array from data loss. XOR parity calculations can only reconstruct the contents of one drive if all the rest are healthy. It cannot fill in multiple missing points. When two drives failed simultaneously, the RAID controlled didn’t even know where to begin.
If the client had used their hard drives to set up a four-drive RAID-6 array, instead of a three-drive RAID-5 array with one hot spare, they would have had the same total capacity available and been able to withstand the failures of both drives without their server crashing. RAID-6 uses extra parity data so that it can continue to function even if up to two hard drives in the array fail. Perhaps after this Dell server recovery situation, the client will consider switching to RAID-6.