3-2-1 backups
Three copies, two media, one off-site. Immutable or offline beats a snapshot the ransomware also encrypted.
3-2-1 is a durability pattern: three copies, two kinds of media, one copy off-site. It is not a ransomware strategy unless one copy cannot be reached with the same credentials as production.
Test restores on a calendar. Time how long until the business can work. That number is your real RTO, not the slide.
Essential Eight includes regular backups for this reason. A backup that has never been restored is a hope.
Fact source: ASD's ACSC glossary. Wording is Cyberstack's.