Login to Server via SSH.

Install lshw

yum install lshw

Check disks:

lshw -class disk -short

This command will show the device name of disks.

Get host uuid:

xe host-list

Create/Attach disk:

xe sr-create content-type=user device-config:device=<device-name> host-uuid=<host-uuid> name-label="Disk-Label"  shared=false type=ext

This will return new disk uuid and now you will be able to see the disk with the label in Storage section of your Xen Center or XCP-ng Center