Windows Server Backup - How does it handle Multiple Backup Disks Online?

[xPETEZx]

Hey Guys,

 

Struggling to find solid confirmed information.

 

I am running Windows Server Backup and have 2x backup disks added.

Both are currently connected.

 

I cant find anywhere what the expected behaviour should be. IE. will the server just keep using 1 disk till its either full or removed?

Does it alternate between the 2 disks?

 

Short of removing 1 disk is there a way to control this? (IE alternate disks with days?)