Create a DB_File on the disk itself.

When you attach a USB HDD with music, the database for this disk is being created.
Judging by the settings in mpd.conf, DB file is created in the system itself, not on a connected USB disk:

# Volumio MPD Configuration File
# Files and directories 
music_directory		"/var/lib/mpd/music"
playlist_directory		"/var/lib/mpd/playlists"
db_file			"/var/lib/mpd/tag_cache"

If you disconnect this disk and attach another disk, the database will be created again, and the database of the previous disk will be erased. This is very wrong. What would it avoid,you must make that the database is created on the disk itself. Tell me how to do it?

It’s not. If you remove a disk then it must be erased from db since it’s not there anymore, and you should not be presented with info about nonexistent music files.

Players on processors Realtek always created base on attached HDD. I have several HDD disks.
Example: I connect any HDD, and it is instantly ready to play, as it does not need to be rescanned! It is logical and convenient.
On Volumio I wait for 10-15 minutes when the any disk is scanned.