Comment 9 for bug 1911900

Ussuri packages are installed and verified (15.2.8-0ubuntu0.20.04.1~cloud0).

In tests for focal and ussuri, rados bench was used to drive some I/O and randomly chosen PGs were repeated deeb-scrubbed in a loop (ceph pg deep-scrub <pg>) to keep scrubbing process run at all times.