Best Config for VMs - Raid 10 - High IO wait

[FcbInfo]

Hi there.
I have 2x e2620, 64gb of ram, 4x1tb 7200rpm raid 10 with cheap raid card.

By using dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync, that gets 190 ~ 210MB/s

What is the best config to the KVM VMs to get low IO wait?
I'm running 3 VMs, that VMs with cPanel, and something about 10 ~ 40 websites (business companies websites, not hard and big databases websites) inside every VM.

That is getting 10 ~ 30% of IO Delay, and i have slow VMs.
My config is with RAW disk file, cache: Write back, and no limits on read or write mb/s and ops/s.

Another question is...
I'm using iotop to try see what is the VM that using more IO.

TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND
1653 be/4 root 0.00 B/s 0.00 B/s 0.00 % 98.21 % [kjournald]
2950 be/4 root 0.00 B/s 0.00 B/s 0.00 % 95.83 % [flush-253:2]


This kjournald and this flush-253:2 never stop. They are always with this 9X%

What is the best values, to use on the limits configurations for a VM work like if it has an 5400rpm disk? Tried to use 50mb/s of limits but for the IO i have no idea.

Thanks for help.

 

[spirit]

you should check if the io delay are for read or write.

For write, you should also check your worload, generaly websites are more random io and sequential.
Try to put cache=none for your vm disk, and use a raid card with write cache.
For read, try to have enough ram in your vm to handle read cache in the vm buffer.

 

[FcbInfo]

It's for read.

+1 for you =P
I have ram a lot without use.

What is the best monitor to see which VM is doing more io delay?

Thanks guy.

 

[spirit]

It's for read.

+1 for you =P
I have ram a lot without use.

What is the best monitor to see which VM is doing more io delay?

Thanks guy.

I think you could start with iostat.

then check bandwith,ios and waits for read/write.

 

[FcbInfo]

Thank you, i'll check it.