Knowledgebase

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