Building a New PC for Music - Part 5: First Problems

A serious problem occurred: the PC suddenly rebooted, without any obvious reason. During startup, the RAID array status description text indicated that there was a problem with one of the disks: an error had occurred. No description about this error, no logging, no debugging. The PC ran fine, but even after several reboots but the error message remained. No idea on how to fix this... I am now very hesitant to install anything else, because the system might completely be wiped out some day...