[libvirt-users] virtual drive performance

[Dominik Psenner]

Hi,

I'm investigating a performance issue on a virtualized windows server 
host that is run on a ubuntu machine via libvirt/qemu. While the host 
can easily read/write on the raid drive with 100Mmb/s as observable with 
dd, the virtualized windows server running on that host is barely able 
to read/write with at most 8Mb/s and averages around 1.4Mb/s. This has 
grown to the extent that the virtualized host is often unresponsive and 
even unable to start up its services with system default timeouts. Any 
help to improve the situation is greatly appreciated.

This is the configuration of the virtualized host:

~$ virsh dumpxml windows-server-2016-x64
<domain type='kvm' id='1'>
   <name>windows-server-2016-x64</name>
   <uuid>XXX</uuid>
   <memory unit='KiB'>2097152</memory>
   <currentMemory unit='KiB'>2097152</currentMemory>
   <vcpu placement='static'>2</vcpu>
   <resource>
     <partition>/machine</partition>
   </resource>
   <os>
     <type arch='x86_64' machine='pc-i440fx-xenial'>hvm</type>
     <boot dev='hd'/>
   </os>
   <features>
     <acpi/>
     <apic/>
     <hyperv>
       <relaxed state='on'/>
       <vapic state='on'/>
       <spinlocks state='on' retries='8191'/>
     </hyperv>
   </features>
   <cpu mode='custom' match='exact'>
     <model fallback='allow'>IvyBridge</model>
     <topology sockets='1' cores='2' threads='1'/>
   </cpu>
   <clock offset='localtime'>
     <timer name='rtc' tickpolicy='catchup'/>
     <timer name='pit' tickpolicy='delay'/>
     <timer name='hpet' present='no'/>
     <timer name='hypervclock' present='yes'/>
   </clock>
   <on_poweroff>destroy</on_poweroff>
   <on_reboot>restart</on_reboot>
   <on_crash>restart</on_crash>
   <pm>
     <suspend-to-mem enabled='no'/>
     <suspend-to-disk enabled='no'/>
   </pm>
   <devices>
     <emulator>/usr/bin/kvm-spice</emulator>
     <disk type='file' device='disk'>
       <driver name='qemu' type='qcow2' cache='none'/>
       <source 
file='/var/data/virtuals/machines/windows-server-2016-x64/image.qcow2'/>
       <backingStore/>
       <target dev='hda' bus='ide'/>
       <alias name='ide0-0-0'/>
       <address type='drive' controller='0' bus='0' target='0' unit='0'/>
     </disk>
     <disk type='file' device='cdrom'>
       <driver name='qemu' type='raw'/>
       <source 
file='/var/data/virtuals/machines/windows-server-2016-x64/dvd.iso'/>
       <backingStore/>
       <target dev='hdb' bus='ide'/>
       <readonly/>
       <alias name='ide0-0-1'/>
       <address type='drive' controller='0' bus='0' target='0' unit='1'/>
     </disk>
     <controller type='usb' index='0' model='ich9-ehci1'>
       <alias name='usb'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x05' 
function='0x7'/>
     </controller>
     <controller type='usb' index='0' model='ich9-uhci1'>
       <alias name='usb'/>
       <master startport='0'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x05' 
function='0x0' multifunction='on'/>
     </controller>
     <controller type='usb' index='0' model='ich9-uhci2'>
       <alias name='usb'/>
       <master startport='2'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x05' 
function='0x1'/>
     </controller>
     <controller type='usb' index='0' model='ich9-uhci3'>
       <alias name='usb'/>
       <master startport='4'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x05' 
function='0x2'/>
     </controller>
     <controller type='pci' index='0' model='pci-root'>
       <alias name='pci.0'/>
     </controller>
     <controller type='ide' index='0'>
       <alias name='ide'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' 
function='0x1'/>
     </controller>
     <interface type='bridge'>
       <mac address='52:54:00:0e:f2:23'/>
       <source bridge='br0'/>
       <target dev='vnet0'/>
       <model type='rtl8139'/>
       <alias name='net0'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' 
function='0x0'/>
     </interface>
     <serial type='pty'>
       <source path='/dev/pts/1'/>
       <target port='0'/>
       <alias name='serial0'/>
     </serial>
     <console type='pty' tty='/dev/pts/1'>
       <source path='/dev/pts/1'/>
       <target type='serial' port='0'/>
       <alias name='serial0'/>
     </console>
     <input type='tablet' bus='usb'>
       <alias name='input0'/>
     </input>
     <input type='mouse' bus='ps2'/>
     <input type='keyboard' bus='ps2'/>
     <graphics type='vnc' port='5900' autoport='yes' listen='127.0.0.1'>
       <listen type='address' address='127.0.0.1'/>
     </graphics>
     <video>
       <model type='vga' vram='16384' heads='1'/>
       <alias name='video0'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x02' 
function='0x0'/>
     </video>
     <memballoon model='virtio'>
       <alias name='balloon0'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' 
function='0x0'/>
     </memballoon>
   </devices>
   <seclabel type='dynamic' model='apparmor' relabel='yes'>
     <label>libvirt-XXX</label>
     <imagelabel>libvirt-XXX</imagelabel>
   </seclabel>
</domain>

Cheers,
Dominik