My venerable late 2015 27 inch iMac died - or at least the hard disk did. So I managed to find from the Apple Refurbished Store a 2019 27 inch iMac which is the last machine that Apple made that can run 32 bit applications since it will boot up in Mojave (10.14.6) - which for the moment I still need. But it came with Big Sur - v 11.6.1.
My backup system is pretty basic - External SATA (formatted in Mac OS Journaled) drives in Intatek docking stations - not high tek but works for me. So I have two drives connected via USBC to the new iMac and drag 74GB of files to a new disk via the finder and it says that it will take 7hours to copy. After 5 minutes I believed it. Booting up in Mojave and copying the same files again it took 7 minutes. I did clone a 4TB via Super Duper in Big Sur - it took close to 48 hours to finalise.
I am now cloning the same drive via Mojave - same drives (well an extra drive as a backup) and to date SuperDuper has been running for 90 minutes and has copied 716GB at a reported 132 Mb/s. So what is going on with Big Sur - I have noticed that saving files of about 240MB via Photoshop is also painfully slow.
Any one else experiencing this - would updating to new operating system help, but this is absurd.
Any thoughts