I plan to use an external RAID storage to backup my most important data into the cloud. The filesystem I want to use is ZFS (OpenZFS for Mac).
So I made a test with Carbon Copy Cloner that I use for backup to my NAS to check if there is a speed difference backing up to ZFS and APFS.
Yes, there is. When I backed up a 14 GB folder to the external SSD drive that was formatted to ZFS it took 3 minutes to backup the folder. When I backed up the same folder to the same external SSD drive formatted to APFS it took 2 minutes and 16 seconds to finish the backup.
If you are asking why do I want to use ZFS and a RAID external storage, the answer is simple: data integrity. And for that ZFS is the best filesystem. Thanks to ZFS and the dual drive in the external storage I will be able to checksum my data and repair the damaged data.
I did not decide yet if I will use ZFS send from the NAS (running FreeBSD) to the external drive or vice versa.
The external drive I will use is Lacie Rugged RAID Pro.