Virtual Disk Performance

[tobru]

Hi,

I installed Proxmox VE 0.9 on a IBM System X 3400 Server. After doing some disk performance tests on a Ubuntu VM and on the host system, I get the following results:

bonnie++ -d /tmp -m host -u nobody

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
host             8G 49148  91 52629  16 24877   7 48690  81 56323   6 210.1   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
host,8G,49148,91,52629,16,24877,7,48690,81,56323,6,210.1,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

sudo bonnie++ -d /opt -m guest -u nobody

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
guest            3G 19478  70 22949  10 16811   9 26825  60 43661  10 238.2   6
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16  2889  97 +++++ +++ +++++ +++  3013  97 +++++ +++ 10157  92
guest,3G,19478,70,22949,10,16811,9,26825,60,43661,10,238.2,6,16,2889,97,+++++,+++,+++++,+++,3013,97,+++++,+++,10157,92

As you can see, I get very poor disk performance on the guest, compared to the host.
Here is the kvm command-line of the guest:

/usr/bin/kvm -monitor pty -vnc unix:/tmp/qemu-server-vnc-101.socket,password -usbdevice tablet -name guest -k de -drive file=/var/lib/vz/images/vm-101-default.qcow2,index=0,if=ide,media=disk -drive file=/var/lib/vz/images/vm-101-opt.qcow2,index=1,if=ide,media=disk -drive index=2,media=cdrom -m 1536 -net nic,model=rtl8139 -net tap

What can I do to tweak the guest disk performance?
Why is the guest running with the disks attached as IDE? Can this be changed to SATA or something else?

Any help is appreciated...

Thanks,
Tobias

 

[dietmar]

What can I do to tweak the guest disk performance?

I guess the best way is to use paravirt hd driver, but we do not support that in 0.9 - sorry.

Why is the guest running with the disks attached as IDE? Can this be changed to SATA or something else?

AFAIK ide is the suggested config. But you should post such questions to the kvm mailing list. They have deeper knowledge about the kvm internals.

- Dietmar

 

[tom]

What can I do to tweak the guest disk performance?
Why is the guest running with the disks attached as IDE? Can this be changed to SATA or something else?

Any help is appreciated...

Thanks,
Tobias

Hi,

Why do you use KVM for Ubuntu guests? Try using OpenVZ - you have NO virtual disks and therefore no performance lost.

The openVZ project already released Ubuntu templates. just download them and upload via web interface to the Proxmox VE.

I just visited your quite nice web site. You run Zimbra and Zimbra is known to work without any issues on OpenVZ. see this post in the zimbra forum.

 

[tobru]

Hi,

Thanks for your replies!
I'll have a look at OpenVZ, it sounds promising.
As I don't know OpenVZ by now, I used KVM. But now I will get familiar with OpenVZ... =)

Regards,
Tobias

 

[tom]

Hi,

Thanks for your replies!
I'll have a look at OpenVZ, it sounds promising.
As I don't know OpenVZ by now, I used KVM. But now I will get familiar with OpenVZ... =)

Regards,
Tobias

Hi Tobias,

see this paper from HP why you should move to OpenVZ

Performance Evaluation of Virtualization Technologies for Server
Consolidation