Thanks! I will test this.Hello,
pve6-usb-automount uses the mount option "sync" for mounting drives. This means no caches or other optimations are used for write operations. This can be especially slow on mechanical drives. The benefit is when the write process finishes the data was really written on disk and not in some cache. This is enabled by default to avoid data loss when someone just unplugs the drive.
You can try to enable async mode in the /usr/bin/pve6_usb_automount.py script. Just search for -o sync and change to async or delete this section and restart the pve6-usb-automount service, then unplug and plug in your disk again. You can see the mode by running the mount command.