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virtual disks perfermonca <=2MB/s

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Hello.

I already wrote to qemu mail list and didn't find an answer.

I've setup qemu / kvm on Debian Wheezy to host some Debian Jessie guests.
I create disk like this:

virsh vol-create-as --pool default --name root.vhd --capacity 50G --format vpc

Then create a virtual with this:
virt-install --connect qemu:///system \
--ram 2048 \
--vcpus=4 \
--cpuset=auto \
--pxe \
--os-type linux \
--boot network,hd,menu=on \
--disk vol=default/root.vhd,device=disk,bus=virtio,cache=writethrough \
--network=bridge:br0,model=virtio \
--noautoconsole \
--hvm \
--autostart \
--check-cpu

After setting up the system I've got poor disk performance.
Using

time dd if=/dev/zero of=/tmp/test oflag=direct bs=64k count=16000

I get 1048576000 bytes (1.0 GB) copied, 397.473 s, 2.6 MB/s

I've changed cache to writeback and got 20MB/s with this test. But copying a file to this virtual using samba gives me no more of 2 MB/s.

I've tested network connectivity with iperf and got around 750Mbit/s, which I think is satisfactory.

I will not want to use raw devices, as it is not self expanded and will use whole space regardless of how much real data occupy.

libvirtd (libvirt) 0.9.12.3

Is there a way to increase disk speed to at least 50MB/s ?

As suggested by other to test:

I've created a raw disk of 10GB and attached to VM and mounted it. The speed is same - 2MB.
As per same cifs/samba access to / on the host - the speed is 180MB+, as there are 2 network interfaces in alb bond.

 > time dd if=/dev/zero of=/vdisks/test oflag=direct bs=64k count=16000
16000+0 records in
16000+0 records out
1048576000 bytes (1.0 GB) copied, 0.970587 s, 1.1 GB/s

real    0m0.972s
user    0m0.008s
sys     0m0.856s

/vdisks reside on a raidz2 zfs pool via PCI-E hardware raid used in IT mode to allow ZFS software raid.

 > /usr/bin/kvm --version
QEMU emulator version 1.1.2 (qemu-kvm-1.1.2+dfsg-6+deb7u19, Debian), Copyright (c) 2003-2008 Fabrice Bellard

 > virsh dumpxml YOURVMNAME > tmp.xml
<domain type='kvm' id='10'>
   <name>srv</name>
   <uuid>c23810c8-fe96-12df-5769-5a7a80c3c35f</uuid>
   <memory unit='KiB'>2097152</memory>
   <currentMemory unit='KiB'>2097152</currentMemory>
   <vcpu placement='static'>4</vcpu>
   <os>
     <type arch='x86_64' machine='pc-1.1'>hvm</type>
     <boot dev='hd'/>
     <boot dev='network'/>
     <bootmenu enable='yes'/>
   </os>
   <features>
     <acpi/>
     <apic/>
     <pae/>
   </features>
   <clock offset='utc'/>
   <on_poweroff>destroy</on_poweroff>
   <on_reboot>restart</on_reboot>
   <on_crash>restart</on_crash>
   <devices>
     <emulator>/usr/bin/kvm</emulator>
     <disk type='file' device='disk'>
       <driver name='qemu' type='vpc' cache='writeback'/>
       <source file='/vdisks/root.vhd'/>
       <target dev='vda' bus='virtio'/>
       <alias name='virtio-disk0'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
     </disk>
     <controller type='usb' index='0'>
       <alias name='usb0'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
     </controller>
     <interface type='bridge'>
       <mac address='52:54:00:de:83:2d'/>
       <source bridge='br0'/>
       <target dev='vnet0'/>
       <model type='virtio'/>
       <alias name='net0'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
     </interface>
     <serial type='pty'>
       <source path='/dev/pts/4'/>
       <target port='0'/>
       <alias name='serial0'/>
     </serial>
     <console type='pty' tty='/dev/pts/4'>
       <source path='/dev/pts/4'/>
       <target type='serial' port='0'/>
       <alias name='serial0'/>
     </console>
     <input type='mouse' bus='ps2'/>
     <graphics type='vnc' port='59081' autoport='no' listen='0.0.0.0'>
       <listen type='address' address='0.0.0.0'/>
     </graphics>
     <video>
       <model type='cirrus' vram='9216' 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='0x08' function='0x0'/>
     </memballoon>
   </devices>
   <seclabel type='none'/>
</domain>

Any help please.

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virtual disks perfermonca <=2MB/s Mimiko <vbvbrj@gmail.com> - 2017-02-22 09:20 +0100
  Re: virtual disks perfermonca <=2MB/s Joel Wirāmu Pauling <joel@aenertia.net> - 2017-02-22 09:50 +0100
    Re: virtual disks perfermonca <=2MB/s Mimiko <vbvbrj@gmail.com> - 2017-02-22 14:00 +0100
  Re: virtual disks perfermonca <=2MB/s Darac Marjal <mailinglist@darac.org.uk> - 2017-02-22 15:10 +0100
    Re: virtual disks perfermonca <=2MB/s Mimiko <vbvbrj@gmail.com> - 2017-02-22 15:50 +0100

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