This system, Sun Fire X4800 M2, was originally certified with RHEL 6.0 to a maximum of 2TB of memory. There are new minimum RHEL version requirements if the system is configured with 4TB of memory.
Red Hat Enterprise Linux 6.2
Sun Fire X4800 M2 with 4TB RAM
The minimum supported version of RHEL for a Sun Fire X4800 M2 configured with 4TB of memory is RHEL 6.2.