All the suggestions of using either a USB drive or a NAS are great as long as you have the USB drive or the NAS backed up somewhere off-site. USB drives and mirrored drives in NAS devices can fail, get stolen or lost in a catastrophic event (fire, flood, etc.). I use a Synology NAS for backing up my PCs and my Macs (Time Machine for Macs and ShadowProtect Desktop for the PCs). Imaged based and automatic, I do not worry about losing a hard drive or an entire device as I can do a bare metal restore to new hardware. The difference in my setup is my Synology NAS data is automatically encrypted and synced to a BackBlaze B2 account. In case of the aforementioned catastrophic loss, I still have all of my data located off-site at BackBlaze. I have a little over 1TB of data at BackBlaze costing about $7.00 per month. I also have the option of syncing my data with multiple off-site accounts (Google, S3, Microsoft, etc.) providing more redundancy. No matter what happens to my devices or my on-site backup, my data is safe.