Where to back up my library?

virtual property exchange has good future indeed, because it only requires virtual ownership.

On sale now at best buy. Not gonna beat this at this price/quality. I bought two yesterday.

https://www.bestbuy.com/site/wd-easystore-8tb-external-usb-3-0-hard-drive-black/5792401.p?skuId=5792...

I am using a Synology 214-play with two 4 TB drives in a hybrid RAID configuration. Those two drives are also backed up via Amazon Glacier's cloud service, its about $6 per month for my storage with is thus far around 640 GB. It can be bit slow to backup but it's good peace of mind for sure.

I have a Bluesound Node 2 as my streaming device. But, not unlike you, I was worried about backing up all my digital files I play with the Node 2. I opted for a Western Digital MyCloud 4tb NAS device. This acts as your own personal cloud (basically a HDD you own in your home) that you can save/share files through your own network. Easy to use and can backup any of your files on an additional HDD connected to the Cloud NAS. Works great and is very versatile.
Also the MyCloud is unlike a Cloud service that one pays a monthly fee to use. You own this device. And additionally, if one buys the Aurender, the digital storage is in that device not stored on an external HDD. If the Aurender crashes or becomes obsolete, your music is on the device!!!