Hi Dominik and thx for your reply. The output from mount is:
srvmucext**-pbs on /mnt/datastore/srvmucext**-pbs type zfs (rw,xattr,noacl)
Te datastore and the ZFS FS has been added via the Web-Gui.
So it looks like an issue with ZFS (no more IO wait) and some bug ? Should I just wait for the next PBS update ? But on the CIFS share I found the same issue.
Thx and br, Tom