Good news and/or perhaps already known to many.
It is recommended that you always have a back-up of Nas music files on a external disk, even if your Nas is equipped with two hard disks.
Today I did a test with Hyper Back-Up at Synology Nas
Determination (which is good news):
If you delete an album or folder from the original folder of your NAS, it will also be deleted from your backup disk after a new backup.
If you change the taging of an album on your NAS, it will also be adapted to the album of your backup disk after backup.
I just wanted to report this info
This will depend on your retention schedule for the HyperBackup job. HB does versioned backups, and I think the default is to keep seven versions, but it’s been a while since I last created a new HB job. So in HB Explorer, it will be “gone” when viewing the current version, but the files may still be there on the storage media as part of the older versions retained. Same goes for any metadata tagging changes you make directly to the music files.
@cwichura makes a good point here. Retention settings can be used to control this.
Myself, I have an off-site NAS and use Synology Drive ShareSync to keep music folders in sync between the two NASes at all times, while keeping a third synced backup in Dropbox.
My weekly database backup is stored on the main music NAS, also synced to Dropbox and then downloaded to the off-site NAS using Syno CloudSync.
Paranoid, maybe, but with three copies altogether and redundant disks on both NASes, data salvage becomes a doodle if something nasty hits the fan…