Recently i had to reinstall my old (but still working) server. I have bought Smart Array P400 instead of my old Smart Array E200, added new harddrives (WD Caviar Black 1TB x 2). And there was an issue regarding that on CentOS 7.x (RHEL 7.x) there is no more drivers for that controller. This was bad for me.

I have started to google the internet and have found a solution for this:
https://www.centos.org/forums/viewtopic.php?f=49&t=47011&start=20
and
https://www.centos.org/forums/viewtopic.php?f=49&t=51302&sid=850e80707bfb3db598f2c5be00ae5e51&start=10

Solution was simple:

1. Download drivers from here http://elrepo.org/people/akemi/testing/el7/isos/
2. Add above driver for CentOS 7 during boot process
3. Install CentOS 7

This is the theory, in practice it look like this

1. Download drivers from link provided above
2. Burn it into USB stick via dd command
3. Insert CD/DVD with CentOS 7.x and USB stick into USB port
4. Boot from CD/DVD
5. During boot proces hit ESCAPE key
   

   CentOS 7 Boot Screen

6. Enter command linux dd
   
   

   CentOS 7 Linux dd

7. Now we will see screen like this
   

   CentOS 7 Driver Disk Device Selection (1)

   I have choose [1]

8. Now we have question about choose driver – choose [1]
   

   CentOS 7 Driver Disk Device Selection (2)

9. Now we have loaded the driver
   

   CentOS 7 Select Drivers to Install

   Choose [c]

10. We have loaded the driver and we can proceed with boot
    

    CentOS 7 Extracting KMOD CCISS

    Choose [c]

11. Now CentOS 7.x is booting
    

    CentOS 7 Boot Continues

12. After that i have proceeded with CentOS 7.x installation.

After steps above I was able to install CentOS 7.x on my old HP Proliant ML 110 G5 server with Smart Array P400.