I now installed a Samsung 990 Evo Plus 2 TB SSD and get slightly better speeds. The random R/W test gives 8.7K IOPS at 544 MiB/s and the direct read test around 782 MiB/s. These speeds are actually good enough when used as a NAS. But I wonder how 13K IOPS at 882 MiB/s were obtained in the review at ...