added extra disk to an existing VM, but extra disk doesn't appear on Linux

I have added extra disk to a VM.
Procedure: storage tab on VM menu and then press Add Disk button. select radio button Volatile Disk, fill in 40GB, Disk Type: FS, Filesystem Format: raw, press Attach button.
The Opennebula menu shows 40 GB, Target: sda

Reboot VM
Run scan commands on Centos 7.8:
echo “- - -” > /sys/class/scsi_host/host0/scan
echo “- - -” > /sys/class/scsi_host/host1/scan
echo 1 > /sys/class/scsi_device/0:0:0:0/device/rescan

check if Linux can detectthe disk:
cat /proc/partitions
major minor #blocks name

253 0 41943040 vda
253 1 41941999 vda1
11 0 364 sr0

no sda is listen.

I would like to know why Linux can’t detect the extra disk /dev/sda?

and was that action success? did you check VM logs in sunstone?