Ceph: Solid State Disks (SSDs) are detected as rotational disks (HDDs).

Issue

Solid State Disks (SSDs) are detected as rotational disks (HDDs).

Example:

# ceph osd metadata 0
{
[...]
    "bluefs_db_rotational": "1",    <----
    "bluefs_db_size": "32212254720",
    "bluefs_db_type": "hdd",
[...]
}

On the nodes hosting the OSD, check how the OSD sees the disks

# grep -Hv "zz" /sys/block/sd*/queue/rotational
/sys/block/sda/queue/rotational:1
/sys/block/sdb/queue/rotational:1
/sys/block/sdc/queue/rotational:1

See also KCS Solution #7008833, How does the kernel determine if a SCSI disk is HDD (rotational) or SSD (non-rotational)?