Blue Iris is not really designed to record to the cloud. It can automatically upload clips to an FTP server, but the clips need to be finished writing before the upload can occur. This causes significant delay that might be unacceptable if your goal is to retain footage of an event that causes you to lose your server. And you also need to devise a scheme for automatically deleting old clips from the FTP server, because Blue Iris does not provide that.
You could back up clips to Dropbox or Google Drive or similar by having Blue Iris record into a folder that is automatically synchronized by the storage provider's app. How well this performs is dependent on the app that does the sync.
So depending on your purposes it may be ideal to rent a Windows dedicated server (or a VPS) somewhere and run a second copy of Blue Iris there, configured for absolute
maximum efficiency (especially Limit decoding, direct-to-disc). Have the remote BI access the cameras either via VPN or by port forwarding with a source address restriction that ensures only your remote BI server is able to connect to the cameras. Renting such a server is likely to be at minimum about $40 a month, possibly much more depending on the provider you choose and how much RAM/storage/bandwidth you need.
