[ovirt-users] Bad performance with Windows 2012 guests

Sven Achtelik Sven.Achtelik at mailpool.us
Sun May 3 12:46:45 UTC 2015

Hi Vadim, 

I've tested the performance with CrystalDiskMark from inside the Windows guest. Using Win2k8 R2 I got expected values for my system, about 88 MB/s on 4k random with 32 queues and 500MB/s + sequential writes with 32 queues. Using a Windows 2012 VM on the same system it's only 33MB/s on 4k random with 32 queues and 300MB/s sequential writes. Similar tests with a linux VM show a bit better values than the Win2k8 R2 and respond ultra-fast.

My hosts are connected via iSCSI using a 10 GbE link and a ZFS appliance as the storage system. All tests have been run several times with the same results.


-----Ursprüngliche Nachricht-----
Von: Vadim Rozenfeld [mailto:vrozenfe at redhat.com] 
Gesendet: Sonntag, 3. Mai 2015 14:35
An: Sven Achtelik
Cc: Doron Fediuck; Martijn Grendelman; Karen Noel; users at ovirt.org
Betreff: Re: AW: Bad performance with Windows 2012 guests

On Sun, 2015-05-03 at 06:48 -0500, Sven Achtelik wrote:
> Hi Doron,
> I've also noticed that there seems to be a difference in performance between Win2k8 R2/Linux and Windows Server 2012. After reading Martijns post I've done some speed test regarding the drive speeds and was looking for a way to compare the VMs on a more professional way. My tests showed, that on the same hardware, the Win2k8 R2 was faster in response and throughput on the disks. I found a utility that somehow measures the latency on a system and that also showed a significant difference. What is the correct way to do a performance test on a VM running in KVM ? 
> Sven
Hi Sven,

Can you specify the type of disk on your system - ide, virtio-blk, or virtio-scsi?
We usually use iometer for disk performance profiling. Sequential read/write, block size from 4K up to 256K, queue depth from 1 to 64.
> -----Ursprüngliche Nachricht-----
> Von: users-bounces at ovirt.org [mailto:users-bounces at ovirt.org] Im 
> Auftrag von Doron Fediuck
> Gesendet: Samstag, 2. Mai 2015 10:50
> An: Martijn Grendelman
> Cc: Karen Noel; users at ovirt.org; Vadim Rozenfeld
> Betreff: Re: [ovirt-users] Bad performance with Windows 2012 guests
> On Apr 30, 2015 14:03, Martijn Grendelman <martijn.grendelman at isaac.nl> wrote:
> >
> > Hi,
> >
> > Ever since our first Windows Server 2012 deployment on oVirt (3.4 
> > back then, now 3.5.1), I have noticed that working on these VMs via 
> > RDP or on the console via VNC is noticeably slower than on Windows 
> > 2008 guests on the same oVirt environment.
> >
> > Basic things like starting an application (even the Server Manager 
> > that get started automatically on login) take a very long time, 
> > sometimes minutes. Everything is just... slow.
> >
> > We have recently deployed Microsoft Exchange on a Windows Server 
> > 2012 guest on RHEV, and it doesn't perform well at all.
> >
> > I haven't been able to find the cause for this slowness; CPU usage 
> > is not excessive and it doesn't seem I/O related. Moreover, other 
> > types of guests (Linux and even Windows 2008) do not have this problem.
> >
> > We have 3 different environments: 
> > - oVirt 3.5.1, on old Dell servers with Penryn Family CPUs with 
> > fairly slow storage on replicated GlusterFS, running CentOS 6.6
> > - oVirt 3.5.1, on modern 6-core SandyBridge servers with local 
> > storage via NFS, running CentOS 7.0)
> > - RHEV 3.4.4 on modern 10-core SandyBridge servers with an iSCSI SAN 
> > behind it, running on RHEV Hypervisor 6.5
> >
> > All of these -very different- environments expose the same behaviour: 
> > Linux, Windows 2008 fast (or as fast as can be expected given the 
> > hardware), Windows 2012 painfully slow.
> >
> > All Windows 2012 servers use VirtIO disk and network. I think all 
> > drivers are from the virtio-win-0.1-74 ISO.
> >
> > Does anyone share this experience? 
> > Any idea why this could happen and how it can be fixed? 
> > Any other information I should share to get a better idea? 
> >
> > Btw, for the guests on the RHEV environment, we have a case with 
> > RedHat support, but that doesn't seem to lead to a quick solution, 
> > hence I'm writing here, too.
> >
> > Thanks for any help. 
> >
> > Regards,
> > Martijn Grendelman
> Hi Martijn,
> Can you please provide the QEMU command line, together with kvm and qemu version?
> This information will be helpful for reproducing the problem. However, if the problem is not reproducible on a local setup, we will probably need to ask collecting some performance information with xperf tool. 
> Doron
> _______________________________________________
> Users mailing list
> Users at ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users

More information about the Users mailing list