I did a backup, copying from my external HDD whose grub died (see the case Boot EFI stopped working in a removable external HDD on Mac mini) to my laptop's HDD (observe it has a SSD formatted as ext4 with Manjaro). Copying a folder of 220 MB from the external HDD to laptop's HDD took only few minutes, thanks to SSD.
After having reinstalled my external HDD, but copying a folder of 220MB from my laptop's HDD to my external HDD, it took 3 hours! I did not understand.
Observe that external HDD and laptop's HDD are both ext4.