The way the Nucleus keeps its OS operational prevents the user from doing changes like this on a permanent basis. With the next update at the latest user additions / manipulations to the OS would be lost. It may be even not persistent between reboots … I would have to consult the Nucleus whitepaper which I’m too lazy to do right now. 
There are advantages to sync, not least that the secondary drive is directly usable, while some backup systems create an optimized data structure that can’t be used directly, it must be “restored” which introduces the possibility of error.
That said, sync is problematic. My Synology NAS has a sync function, and when I went to set it up it offered me two choices for when a file disappears from my computer:
- Delete the file from the NAS as well. NOOOO, then an accidental fumble-finger delete would be unrecoverable. Plus it would be impossible to recover space on the computer by deleting not recently used files, because the archived copy would be lost as well.
- Restore the computer’s file from the NAS. NOOOO, then it would be impossible to free up space on the computer.
The problem is that sync tries to maintain the two stores in the same state. That’s not what you want.
Consider a Roon case: you a have ripped CD, in Roon and backed up, you buy a high res version, you don’t want to keep the CD rip in the active Roon library anymore, but you d9nt want to lose it forever, just because. I never throw away anything. Sync would prevent that.
I don’t want anything 
It was just my understanding that @Mikael_Ollars want’s that and I was trying to imagine something that will work for him (and as per @anon47919701 saying it is not going to work with ROOK). I said somewhere above that the backup (mirroring, synchronizing whatever) it’s not a simple task, but these days people just want one button to rule them all ignoring the fact that sometime it helps to know a thing or two! Just another thought.
For sure, but a backup is indeed a sync between the source and the target.
And i appreciate all of the suggestions and considerations, it would still be of great assistance to the computer illiterate who bought a Nucleus, the button or function that backs up both the database and the local media files. For consistency, and for not needing a separate computer running.
Nope, it’s quite dangerous to consider a synced copy as a backup. Consider this: files are accidently deleted from the source store, then the deletion is synced to the target store. Boom, no more files to recover from … ouch!
File Synchronization and File Backup have very distinct purposes … members commenting on here about it are not trying point score or being pedantic … their comments are to clarify the requirements and avoid later issues.
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Well, there’s sync and then there’s sync… My Allway Sync application allows for variations, e.g. allow or prevent the propagation of deletions from the master to the slave. I’ve set it to not propagate deletions to avoid the issue you mention.
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Yes, i am fully aware of this. But still, a backup that does not syncronize the target with the current contents of the source is not much of a backup, right?
I have been working in IT solutions for the last 30years so i do have a pretty good idea what a backup is. The rest is semantics
Hi @Geoff,
I’m also aware of tools that allow that, but if those options are enabled then it not really syncing anymore, it’s creating a cumulative backup. I just did not want to cloud the argument.
As @Mikael_Ollars points out it’s a matter of semantics, but semantics do matter when attempting to understand the requirements.
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Hi Geoff
This would be really useful for me too. I have even bought a disk thinking it must be possible. I have an internal SSD in my Nucleus. I’d like to plug in my external USB SSD and administer or schedule the back up using the Roon web interface. That would be perfect!
That said the internal SSD storage on my Nucleus is actually my iTunes library, mostly ALAC files from CDs. It works fine and data is data after all. On another front I currently add to this library via iTunes burning CDs from an external drive plugged into my Mac. I would want to keep this work around since I use iTunes to sync my library with my iPhone so I have all my library there as well albeit it at a lower resolution.