[libvirt-users] VM Performance using KVM Vs. VMware ESXi

[Matt Schumacher]

Jatin,

Using qemu without the virtio scsi and nic drivers is like running 
vmware with ide disks and e1000 nic instead of LSI disks and vmxnet3 
nics, it forces the system to emulate completely different hardware.

In linux the virtio drivers are implemented in the kernel, so you either 
need a new kernel or the virtio kernel modules.  I'm not sure which for 
RHEL5, but I suspect you can get what you need with the kmod-virtio 
package, then rebuilding the initrd image to load the modules at boot.

Keep in mind that sda will change to vda, which on some linux distros 
requires updates to the bootloader and inittab, but redhat uses 
filesystem labels if I remember correctly, so it should just work.

Please let us know how the benchmarks look after you get virtio working, 
I'm curious...

schu


On 4/14/2015 5:33 AM, Jatin Davey wrote:
> Thanks Dominique & Daniel.
>
> Looks like i need to upgrade my VMs kernel to make it aware of virtio.
>
> Found this information from this link:
>
> http://wiki.libvirt.org/page/Virtio#Disk_.28block.29_device_driver
>
> I tried without upgrading the Kernel and as soon as i start my VM it 
> got into Kernel Panic. I will try using virtio after upgrading my VMs 
> kernel.
>
> Thanks for all the responses and pointers.
>
> Thanks
> Jatin
>
> On 4/14/2015 5:08 PM, Dominique Ramaekers wrote:
>> Please read:https://libvirt.org/formatdomain.html
>>
>>
>> -----Oorspronkelijk bericht-----
>> Van: Jatin Davey [mailto:jashokda at cisco.com]
>> Verzonden: dinsdag 14 april 2015 13:39
>> Aan: Daniel P. Berrange
>> CC: Dominique Ramaekers;libvirt-users at redhat.com
>> Onderwerp: Re: [libvirt-users] VM Performance using KVM Vs. VMware ESXi
>>
>> On 4/14/2015 4:58 PM, Daniel P. Berrange wrote:
>>> On Tue, Apr 14, 2015 at 04:53:52PM +0530, Jatin Davey wrote:
>>>> On 4/14/2015 4:42 PM, Dominique Ramaekers wrote:
>>>>> About Spice: I think it's good practice to use spice because it
>>>>> improves the performance of the VM in general by improving screen
>>>>> performance. If your VM is constantly displaying output, you'll
>>>>> probably will notice a difference.
>>>>>
>>>> [Jatin] Ok, This is not my concern as of now. I will take a look at
>>>> it sometime later.
>>>>> About virtio: You can see it in the settings. Better yet, it's in
>>>>> your XML. If you post your XML, we can take a look...
>>>>>
>>>> Here is the xml associated with my VM:
>>>>
>>>> ********************************
>>>> <domain type='kvm'>
>>>>     <devices>
>>>>       <emulator>/usr/libexec/qemu-kvm</emulator>
>>>>       <disk type='file' device='disk'>
>>>>         <driver name='qemu' type='qcow2' cache='none'/>
>>>>         <source file='/var/lib/libvirt/images/****.qcow2'/>
>>>>         <target dev='hda' bus='ide'/>
>>>>         <address type='drive' controller='0' bus='0' target='0' unit='0'/>
>>>>       </disk>
>>> This disk is configured to use IDE, so performance of anything that
>>> does disk I/O is going to be terrible. You really want to be using virtio.
>>>
>>>>      <interface type='bridge'>
>>>>        <mac address='52:54:00:c9:58:c9'/>
>>>>        <source bridge='br332'/>
>>>>        <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
>>>>       </interface>
>>> This doesn't have any model listed at all, so it will be falling back
>>> to a generic emulated NIC. Again performance of this is likely going
>>> to be terrible for anything doing network I/O. You want to be using
>>> virtio for this too.
>>>
>>> Regards,
>>> Daniel
>> How do i make use of virtio for the both disk and network that you have mentioned above ?
>> Any pointers to it would be helpful.
>>
>> Thanks
>> Jatin
>
>
>
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