Autotest doesn't install the OSD packages for the in-memory OSD. Instead, it appears to default to installing only ldiskfs. For example, see https://testing.whamcloud.com/test_logs/70b4678d-7f48-4e27-acc4-f7691bb4e47f/show_text. I used `rpm -qa` to list all installed packages - and I only see ldiskfs OSD packages:

kmod-lustre-osd-ldiskfs-2.16.50_88_gad94a0a-1.el8.x86_64

lustre-osd-ldiskfs-mount-2.16.50_88_gad94a0a-1.el8.x86_64

Notably, the $FSTYPE environment variable is set correctly. To reproduce this, copy https://review.whamcloud.com/c/fs/lustre-release/+/55594 revision 22. This version of patch includes the OSD along with the debugging I added. For test parameters, I used:

Test-Parameters: trivial fstype=mem testlist=sanity