Thanks for that, and sorry to ask more questions...

I'm using this as a backup of last resort, that I hopefully will never need to use, so planned on using Cold storage to minimize costs.

So if running an Image backup of the system drive, and just using weekly Full/Synthetic Backups, and recognizing that Cold storage requires a minimum retention of 90days to avoid deletion penalties, does that mean I should set the backup retention policy to also be 90days+ - or are those two things unrelated.

I suspect the link you provided may have the answer, but it required login credentials.

Thanks for the detailed response - very helpful.

One area I'm still unclear on, is backing up an image of the system disk to Azure.

Lets say I want to keep a system-disk image in cloud that is updated on a weekly basis, for disaster recovery.

Obviously, there needs to be an initial full backup taken, and that will take a long time to run,

After that I suspect that block-level incrementals can be added, but for how long can/should you continue to do that, to avoid another full backup ? - monthly, yearly ?

Also, presumably you don't want a retention policy that could delete files that block-level incrementals might rely on... so does that mean don't delete ? or what ?