Install memtester-4.2.1-1.el6.x86_64 and memtest86+-4.10-2.el6.x86_64 (or updated versions).

<code>
# memtest-setup
# memtester 500M
# memtester 10G 2
</code>

Check output.

Also look at the 'sar' program.  Files in /var/log/sa.

Example run:

<code>
sar -f /var/log/sa19
</code>