Retention periods
To size any backup storage, how long data is kept must be known. Some thought should be put into defining retention periods. Important considerations include:
What regulatory requirements exist for data retention that must be met by the backup system.
What SLAs are present.
How long does data need to be retained to properly recover from a ransomware attack. Ransomware often installs in the environment and sits dormant for a period, which should be considered.