The cloud failover appliance (CFA) is not set up to make copies of the archive disks. For this, you will need to import jobs from the archive disk back to the CFA, insert a new disk, and then archive them again.
Turn off job recycling via Jobs › Settings › Automatic Job Management.
Otherwise the CFA will see the old jobs and immediately begin to recycle them.
Once this is done you will need to insert the old archive disk:
Click View Archive Jobs and verify that there is enough space on the RAID for the jobs you would like to copy over.
Select each, and then select Import Selected Archive Jobs.
You will need to wait for each job to finish importing that will show in Server › Importing Jobs.
When this is finished you can use Prepare for Removal on the old archive disk, then insert the new one.
Once the disk is recognized, jobs can be copied over via Archive › Libraries by choosing the Archive Jobs button (if you do not see this button, chances you will need to Clear Archive Processes).
This will display a list of jobs currently on the RAID that you can then select and archive.
Remember to select Automatic Job Management again to recycle the old jobs from the RAID.