If you struggled to cope with disk I/O on virtual host machines which runs on Centos or RHEL, there is a great system performance tuning tool named TUNED, comes with different profiles.
for installing tuned;
yum install tuned -y
starting the service permanently;
service tuned start chkconfig tuned on service ktune start chkconfig ktune on
status of running profile;
tuned-adm active
list of profiles;
tuned-adm list
setting the profile for disk I/O optimization;
tuned-adm profile virtual-host
if you want to disable defined profile (i don’t thing you will consider this :);
tuned-adm off
You are going to see significant optimization on atop tool. Here are tuned profile summary;
| tunable | default | enterprise storage | virtual host | virtual guest | latency performance | throughput performance |
| kernel.sched min granularity ns | 4ms | 10ms | 10ms | 10ms | 10ms | |
| kernel.sched wakeup granularity ns | 4ms | 15ms | 15ms | 15ms | 15ms | |
| vm.dirty ratio | 20%ram | 40% | 10% | 40% | 40% | |
| vm.dirty background ratio | 10% ram | 5% | ||||
| vm.swappiness | 60 | 10 | 30 | |||
| I/O Scheduler (Elevator) | CFQ | deadline | deadline | deadline | deadline | deadline |
| Filesystem Barriers | On | Off | Off | Off | ||
| CPU Governor | ondemand | performance | performance | performance | ||
| Disk Read-ahead | 4x |