Create new backup copy job

[perjonsson1960]

Folks,

We have a primary GFS backup of our physical file server cluster (two nodes) with four weekly, 12 monthly and 2 yearly backups.
What happens if I create a backup copy job with mirroring? Will it copy only the latest full backup plus the incrementals after it (if any), or will it copy the entire backup?
The full backup files are approx. 23 TB in size.
I don't want it to copy the data twice, since it is a cluster.
Is it better to choose pruning in this case?

Kind regards,
PJ