Time for occ filescan on external storage

I use Nextcloud 16 on an Ubuntu 18.04 machine.
This machine is an older 6-core AMD Phenom with 8GB RAM.
I use an internal 4TB ext4 formated SATA harddrive as external storage. The external storage is synced via rsync from 2 different locations.
Right now there are round about 60k Folders and 100k files on the drive - taking 170GB.

OCC Filescan is taking 2 days now, while mysql is using 80% and apache2 20% CPU.

mysql error.log is empty
apache2 error.log is empty
nextcloud.log shows a LockWaitTimeoutException every now and then. I suspect because of the busy mysql server.

Is this normal behavior? Does anyone has experience with a similar setup? All I found on the forum or the internet where statements like “could take a while” or something like that.