One of the options is directory caching on file systems, introduced in WB 3 if I remember correctly. If you have a very large partition with billions of little files on it, the Amiga grinds to a halt trying to cache it all.
Which was meant for floppies afaik. I remember I once created a HDD boot partition unintentionally with FFS-DC on OS 3.9 and it did continuously show read errors until I found the culprit to be that filesystem. Changing it to FFS stopped the errors immediately.
