More Memory Than Sense

My recent bugbear is - servers with inaccessible memory.

You go and spec a nice new server with say 8Gb of RAM (a little box), you install Debian, you start adding applications to the machine and then a couple of months later some anal sysadmin comes along, does a free -m and mutters about under-specced virtualization servers when he sees

             total       used       free     shared    buffers     cached
Mem:          3287        225       3062          0         24        149

For those of you not paying attention - the machine isn’t using over half of it’s memory. So first of all how do you spot this and secondly how do you fix it?

If you’re on Debian then the spotting is easy (for some hardware) - apt-get install lshw and then run lshw -class memory | grep -A 4 ‘-memory'. If the size is bigger than the total from free` then you’ve got wasted resources.

The fix? Install the right bigmem kernel. And then recompile VMware server. Dammit.