Red Hat Enterprise Linux 64-Bit Support
Red Hat Enterprise Linux 6 supports 64-bit processors; these processors can theoretically use up to 18 exabytes of memory. As of general availability (GA), Red Hat Enterprise Linux 6 is tested and certified to support up to 8TB of physical memory.
The size of memory supported by Red Hat Enterprise Linux 6 is expected to grow over several minor updates, as Red Hat continues to introduce and improve more features that enable the use of larger memory blocks. Examples of such improvements (as of Red Hat Enterprise Linux 6 GA) are:
Huge pages and transparent huge pages
Non-Uniform Memory Access improvements