I guess if you have many overlapping files on both drives and you force rsync to actually look inside and compare them, its efficiency might suffer? It wasn't j

I guess if you have many overlapping files on both drives and you force rsync to actually look inside and compare them, its efficiency might suffer? It wasn't just a simple copy from one full drive to another empty one, rather two drives with overlapping files that had to be synced. I experimented with rsync to see if I could replace RAID with it, i.e. one primary drive, one backup drive synced on the background instead of mirroring directly (and getting the same low-level bugs spread to both drives or getting both drives to die at around the same time). Both drives were encrypted on the device level (dm-crypt AES128) with standard ext4 on top of mapped drive. I previously ran configs with RAID-1 as well as BTRFS RAID-5 (horribly buggy and dangerous) and wanted to see if rsync makes sense for this purpose (it doesn't). I couldn't use ZFS as that NAS didn't have ECC.