Issue : You can not install Xenserver 5.5 on an IBM 3850 X5 and the install gives an error about can not detect the local disks.

Resolution :

Im afraid the only resolution is to install Xenserver 5.6. Xenserver 5.5 will not install because the array controller in the IBM 3850 X5 server is not supported, But it is supported in Xenserver 5.6.