@enealDC
there is an automated check once a month.
what do you mean with rebuild settings to high?
there no setting on the adaptec that allow me to change something like this.

we changd the controller on both dss machines.
because of compatibility of raiddata we use on the first DSS another adaptec (51645).
on the second we use now areca.

but after 3 weeks we have no idea wy this happend.
no answer from open-e and no answer from adaptec.