Gerard,

Your system looks fine. Linux utilizes the free/unused memory to cache data, and hence the free memory reported might seem very low, but it's being used by the kernel to actively use it for caching. As/When it's needed, the kernel releases memory for the processes to use, so this is normal. If you want to look at what processes are using the most memory try this command:

ps auwwwx | awk '{print$4"\t"$11'} | sort | uniq -c | awk '{print $2" "$1" "$3}' | sort -nr

The output will show you the process with the most memory being used. For example on a test CAM here was the output of the command listed above:

14.3 1 /usr/java/jdk1.6.0_12/bin/java
0.8 1 /usr/sbin/httpd.worker
0.7 1 /usr/sbin/httpd.worker
0.6 1 /usr/sbin/httpd.worker
0.6 1 postgres:
0.5 1 postgres:
0.5 1 heartbeat:

Meaning Java was taking the most memory.

HTH,

Faisal