hello my freinds please help me

i have centos 7 i have 2 disk 2×1.5  i install system on raid0 i want 3 tb not 1.5 tb i want merge my disk anyone help me ?

anyone?

Are you sure you are on RAID 0? Did you checked the configuration of the RAID? Did you added the 2nd HDD after the install of the CentOS?
If both of them was connected on before the installation and you was on RAID 0, then CentOS installation should see them and use both of them. (I`m sure about it because before I was using RAID 0 on my server (now RAID 1+0 and it sees only 1 HDD(second one is for backups))).
If you added the 2nd HDD after the installation you need to add it manually to CentOS (partitions, fs, fstab, ...). A bit annoying job, but nothing special.
Please check and give me answers of the questions I asked so I know how to help you.