RAID Reconstruction, also known as RAID Build, is a process of redesigning and restoring a RAID drive or environment to normal working conditions after its data or drive configuration has been lost or corrupted.
After a disk fails suddenly, a RAID array copies data to a spare drive while the failed one is replaced. Thereafter, the data is re-assembled on the new drive by using algorithms and parity data. RAID reconstruction can also be proactive if the RAID array identifies that a hard drive is about to fail. You may experience that the performance of some of the applications or processes are adversely affected during the RAID reconstruction.
The RAID reconstruction is a time consuming process which is a major concern for storage administrator. Multiple failed drives or higher capacity drives can lead to longer reconstruction time, usually days.