I can´t see my disks on /dev

[ESGLinux]

Hi All,

I have a RHEL server and I have a strange problem with my disks.

First I have two disks in RAID1 (hardware). I see the raid device as
/dev/sda.

I have plugged two new disks but I don´t have made a RAID with them. If I
reboot the machine I see  the four disks detected but I don´t get a device
asociated to the new disks.
If I make dmesg I see the four disks, but  if I make fdisk -l I only see
/dev/sda,

Why can´t I see the new disks?

any help ?

Thanks in advance

ESG