It is since christmas that the storage backbone of digital archive is hanging in the balance. After the crashing of one of the drives, the DiskStation did follow the rescue pat set up: swap in the hot spare disk, beginning reconstruction and consistency checking on the system volume right away.
The system is now using Hot Spare disk (Disk 2) to repair the degraded storage space (Volume 1).
So far so good, but as it turns out along the way part of the system partition got affected, which resulted in the data volume put in a crashed state, where all that is visible is a collection of individual drives, which no longer are assempled into a joint partition. While I now have started to hunt down information on recovery strategies in earnest, one of the obvious things to do is to run an extended test on the drives in the system:
Given we are dealing with 12 drives of approx. 23 TB joint storage space, this might take a while, but on the other hand I do not think it is wise to move too far without getting some health information on the individual components.