Hello Marky,

Sorry to hear you are having issues installing.  I have that exact machine and it installs/performs flawlessly.  I have installed RHEL numerous times (I use it as a Lab system).  I find the UEFI on this hardware somewhat obscure and I wonder if we possibly have different settings which would make the machine behave differently.  Also - did your system previously have another OS installed (i.e. Windows)?  I have, in the past, booted using Knoppix and run Gparted on the RAID drives I have setup (I had issues switching between ESXi and RHEL, for whatever reason).

RHEL is absolutely supported on this hardware platform

http://www-03.ibm.com/systems/x/hardware/rack/x3550m3/specs.html

http://www-947.ibm.com/support/entry/portal/docdisplay?lndocid=migr-5086400

At times I find IBM documentation amazing.  The documentation they have provided regarding RHEL on the x3550 is faily vague though.

I believe firstboot only works when the machine has an operational display and desktop.

You may want to look at the output from

# yum grouplist

and review the "Installed Groups:"

There are a number of logs you can review also

/var/log/anaconda.*

Marky,

I've recently had two cases with customers where the hardware was slightly different ( IBM X3250 M4) but the results were the same. In order to boot the system with a RAID controller card enabled, the system had to be booted in Legacy mode. This only affected how the 64bit iso was handled, and strangely the 32bit iso would work normally.

I suspect that you may be running into a similar issue. The documentation that I tried to find with regard to IBMs support for RHEL with RAID controller support in UEFI mode unfortunately left me at a bit of a loss too. 

Legacy was needed if the controller was RAID. If set to AHCI there were no difficulties installating. I did end up writing a knowledgebase article from our side for this specific hardware:

"IBM x3250 M4 Systems fail to see RHEL x86_64 dvd.iso"

https://access.redhat.com/knowledge/solutions/231773

If this matches a portion of what you're describing, feel free to open a case and have the engineer notify me. If the symtopms match the above we can revise the article to include your hardware model as well.