Thanks.
played yesterday with restic: it seems quick.
tests on i7-6700, 16GB, SSD (target backup medium will be an HDD)
read about borgbackup, indeed they seem very similar.
(some) differences: other programming language and - IIRC- bb. can do backup's
without encryption.
all I need is verification (before (!) needed restore)
maybe I will play with bb. too...