You can also refer below video for details [URL] 
Hello Experts,   we have DELL power edge R930 server, initially it had only one embedded raid controller card with 3 HDD, later we add another raid controller and add add 15 more HDD in it.  we able to see the both the raid controller card into bios, everything seems fine.  but while booting it gives us some error and ask us to press f1 to continue........and other options. if we press f1 it boots normal but someone has to press f1 before it boots. so i disabled F1/F2 prompt from the bios now its boots but still its show the error on the booting screen. I have attached the screenshot of the error as well.  fyi....we have four servers and we did this same into four server and all of them are having same issue.  Now, 1. is there any issue if bring this server in production as its booting normal apart from this error? is it so critical?  2:- is there any way we can clean this error msg from the screen? what can we do to resolve it?   thanks in advance. [IMAGE]
Dell R930: CBL 0003: backplane 2 connector a0 disconnected