(In reply to comment #0)
> Comment: an absent drive should not be confused with 'deleted files'.

Squeezebox Server has always worked this way. If a drive goes offline, the content  on it will be removed from the library during a scan.

It does not have to be scan, all specified folders must be avaible to the server all the time, when it is running.
If drive is absent during startup, the dB may be wiped too, I'm unsure of which exact circumstance,
It can be if the root folder for your library is absent, then you get the " no muisc folder specified " error and the dB is wiped.

I have no idea on whats the design rationale behind it, I'm convinced that it is designed this way for a good reason .

There is probably duplicate bugs for this in bugzilla.

Sugestion, don't consider a specified music folder gone untill user erases it from the settings.
Throw an error message if user tries to play such file or add them to playlists. If a playlist already contains such file , show error message and move on to next file.
I'll give the bug vote mostly to have this explained, maybe the server gets completely dysfunctional with a stale dB .

Now i've figured one reason to why it has to be this way during a scan , if a storage is mounted somewhere deeper in the file structure, there is no way for sbs/lms to actually know if it's just absent or gone forever.
Only the top level case may be possible to fix, all other ways a user may mount storage is unpredicable. And the only safe way is to consider unreachable locations gone.
Or simply remove shortcuts or subfolders, that would have the same effect, the dB would turn out a complete mess.