Goodsync.
It’s very reasonably priced and well worth the cost. I’ve tried nearly all solutions on Mac, PC and Linux. Goodsync just gets everything right, and I’ll never look back.
It’s simple to use, but also goes deep when needed.
Of course if you’re cloud-free, it requires at least one other computer to backup / sync / mirror to. I recommend a hybrid approach. More on this in a bit.
It’s available for Mac, Win and Linux and even works together across a mixture of OSs. It even has iOS and Android support for mobile.
It works without any requirement of the Cloud or internet. It does have a Cloud connection option to help find computers across disparate networks, if desired, but it’s completely optional.
It’s extremely robust and uses true “block-based delta” which means it’s able to sync segments / portions / blocks within a massive file (like audio or video) without having to re-copy the entire file. Only the parts of the file that have changed. This is great for the studio / DAW environment with large audio files.
It has options for automatically syncing one-way (a backup), two-way (a sync).
It’s smart enough to deal with complex chains of computers all syncing with each other, and avoids “cascading” sync issues by automatically pausing the sync or backup job on some of the computers, so they happen in the correct order to ensure conflicts and missed files are avoided.
It also has very advanced conflict resolution options.
It can do the sync/backup automatically on file change (not the option to choose if recording, of course), or on a schedule, or manually.
It has advanced ways to filter what gets synced / backed up. E.g. you can omit files that are temp files, etc. Same with skipping certain folders, etc.
You can create any number of “jobs” so that it can, say, automatically backup on file change, a certain folder, for one job. Another job can then work as schedule-based. This is great for doing things like auto-syncing a mixdown folder to another computer, while still keeping the DAW free of file-change backups in most areas.
It will even do the backup sync using FTP, if you have an internet server. This is great for collab projects. Or client access to files. Or client upload of files (for example a mastering engineer). Have the files the client uploaded to your webserver auto sync to a secure folder on your hard-drive, automatically.
It’s easy to exit out of it completely without pesky background services running, if desired.
And here’s one very cool feature for the DAW environment: Since you can freely choose which computers host the “jobs,” and since the heavy lifting is done on the computer(s) that hosts the jobs, you can configure it so that the DAW is free from the heavy lifting (i.e., DAW not hosting the backup jobs). This results in the least amount of CPU burden on the DAW.
In fact, it’s so good, you could probably sync on file change, even during a recording on not get audio dropouts. I wouldn’t recommend this though, but just emphasizing how much CPU is offloaded on the DAW by configuring it this way. And of course, if you’re using scheduled or manual backups, no CPU is used when it’s not backing up / syncing.
As for my “hybrid” approach, here’s what I’d strongly recommend…
Use Goodsync (or something similar) to do a cloud-less backup to a computer on your network.
Then, backup the backup (to the cloud).
By backing up to the cloud, your backup, you avoid the issue of the lengthy and CPU intensive processing happening on your DAW. It also allows you to reboot the DAW or even power it down, while your mirror is happily backing up online. The end result is that your files get backed up faster (no interruptions).
A true backup solution is one that is backed up in at least two places.
As for which cloud-based backup service to use to back up your Goodsync mirror (if I’ve convinced you of this), is Crashplan. I’ve used most of them (Mozy, Carbonite, Backblaze) and Crashplan is my favorite. No limit on how much you can backup, either.
I actually lost nearly everything, once (before I was creating local Goodsync mirrors) and Crashplan online backup brought everything back.
Final bit of advice, on Mac especially, I would make a bootable backup of your OS, on an external drive, using “Sync Pro X” or Carbon Copy Cloner.
