What does top say is using it all ?
shuld give anoutput like when i looked at my server doing a backup
root@srv41:/# top
top - 21:35:04 up 43 min, 1 user, load average: 1.53, 1.92, 1.93
Tasks: 73 total, 3 running, 70 sleeping, 0 stopped, 0 zombie
%Cpu(s): 14.6 us, 1.7 sy, 0.0 ni, 83.3 id, 0.5 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem: 25165824 total, 7278060 used, 17887764 free, 0 buffers
KiB Swap: 8388608 total, 0 used, 8388608 free. 5399584 cached Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
21562 root 20 0 4440 812 416 R 76.2 0.0 0:02.29 gzip
925 admin 20 0 784392 369236 71260 R 19.6 1.5 5:56.17 apache2
921 mysql 20 0 1287324 64608 8072 S 5.7 0.3 3:37.33 mysqld
941 root 20 0 876584 10772 2928 S 0.7 0.0 0:02.26 fail2ban-server
Bare in mind this was a debian server but it is the same on a centos server.
pleas post output here so we can help