I’ve used ChronoSync (Mac) with success for many years to back up my Macs. I don’t use it currently to backup my music files because they are on a Synology NAS, which has its own backup software, but I still use ChronoSync to sync my travel music selection between the NAS and the microSD for my DAP. ChronoSync is very flexible, a bit complex, but superbly reliable and able to do exactly what you want (partial backups, various forms of sync, and more).
Are you looking for backup software or a better way to replicate your music files on another drive?
Also, what OS is your primary hard drive connected?
On my Linux box I use Duplicacy to backup to a USB drive and Wasabi cloud storage. This is a command line application but it is available with GUI too.
I use rsync from my qnap NAS to backup the music from my USB hdd attached to ROCK/NUC. And secondly I use the jottacloud application from my windows10 latop to sync my music collection to the cloud.
Then you probably want one of the synchronising apps recommended. But remember these do not provide a reliable backup since any changes on the source drive will be replicated on the destination unless there’s a versioning option.
Just checked this out, seem to have a limit in the files that can be processed in the free version (says 40.000 to be processed in 30 consecutive days).
It looks like I more need a tool for synchronization, rather than for backups.
Will give the recommended programs a try and report back on my findings.
A great, great tool I use for database/server stuff at work but use it for all my home tasks as well is “Beyond Compare”. This is one of the greatest utils/apps IMHO. Its not a automated backup util and not its intended function.
Every couple weeks I hook up my ext usb HD to my NAS, run my custom session (saved sync function) which will match the source (NAS) to the destination (ext HD).
I use SyncBack Pro on Windows 10 , once you have a backup it does everything by difference so BU is very quick as long as you aren’t adding or changing a lot
Very stable , been using for years. There’s a freebie too I think