Only 8GB of 16GB RAM is used by Linux?

emacsx · 02-17-2016, 05:00 AM

We have a Dell Xeon quadcore workstation which is installed with 16GB (2x8GB) DDR3 RAM but the Red Hat 5 OS shows only 8GB RAM when observe red in Memory and Swap History of the System Monitor utility. I have also verified the same issue with MS Windows Server 2012 R2 which shows total RAM of 16GB but usable RAM of 8GB.
Looking into the setup of workstation the total installed physical memory is indeed 16GB in two different slots. It was showing only 1 memory channel before but when I swapped the memory modules it is showing 2 memory channels. However, with this configuration the System Monitor utility of Linux is still showing 8GB of RAM.
Why this is happening and, is it a hardware or OS issue?

wpeckham · 02-17-2016, 05:04 AM

Have you checked the mesg output? Where have you looked for clues?

jefro · 02-17-2016, 03:37 PM

Run memtest and see if it reports the memory correctly.

I get the feeling a ram board is bad or set of ram boards are bad. You'd need server memory in this and be sure ecc is set correctly.

sneakyimp · 02-19-2016, 02:06 PM

It's hard to tell from your post if the machine is recognizing the RAM or not. Can you post the output of free -h on the Red Hat machine? On my machine, which has 8GB of RAM, it looks like this:

Code:

$ free -h
             total       used       free     shared    buffers     cached
Mem:          7.3G       3.7G       3.6G        17M       551M       1.0G
-/+ buffers/cache:       2.2G       5.1G
Swap:          29G         0B        29G