A hot-swap rebuild occurs when a controller detects that a failed disk drive in a logical device has been removed and then reinserted.
Gently pull the failed disk drive from the enclosure without fully removing it, then wait for it to spin down fully before continuing.
If nothing is wrong with the disk drive, reinstall it.
If necessary, replace the failed disk drive with a new disk drive of equal or larger size.
The controller detects the reinserted (or new) disk drive and begins to rebuild the logical device.