Open Stack

Hello:
    I  am using openstack + libvirt + qemu-kvm. The speed of copying files between virtual machines exceeds 300M Byte per second but the speed of dd command:
 "watch dd oflag=direct,nonblock if=/dev/zero of=/opt/iotest1 bs=4M count=10"  is around 20M byte per second. Every guest is the same, and there is no io tuning in libvirt. What can I do to unleash the speed of disk io speed inside the guest? 
                                                                                                                                                                                        Thanks!

The libvirt vm xml is as follow:

<domain type='kvm' id='446'>
  <name>instance-00000663</name>
  <uuid>d9bda7d7-f68a-45ea-84a1-f50faa44b801</uuid>
  <metadata>
    <nova:instance xmlns:nova="http://openstack.org/xmlns/libvirt/nova/1.0">
      <nova:package version="13.1.0-1.el7"/>
      <nova:name>smtestiotune</nova:name>
      <nova:creationTime>2017-08-23 07:38:13</nova:creationTime>
      <nova:flavor name="1VCPU_1G-RAM_50G-DISK">
        <nova:memory>1024</nova:memory>
        <nova:disk>50</nova:disk>
        <nova:swap>0</nova:swap>
        <nova:ephemeral>0</nova:ephemeral>
        <nova:vcpus>1</nova:vcpus>
      </nova:flavor>
      <nova:owner>
        <nova:user uuid="cbcec503badc4a4191048b6e948bd926">admin</nova:user>
        <nova:project uuid="160b6ae5b7a645879d5e1fbd67693e8e">admin</nova:project>
      </nova:owner>
      <nova:root type="image" uuid="34714b12-281e-4180-8a6b-d6cd90c40d9c"/>
    </nova:instance>
  </metadata>
  <memory unit='KiB'>1048576</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
  <vcpu placement='static'>1</vcpu>
  <cputune>
    <shares>1024</shares>
  </cputune>
  <resource>
    <partition>/machine</partition>
  </resource>
  <sysinfo type='smbios'>
    <system>
      <entry name='manufacturer'>Fedora Project</entry>
      <entry name='product'>OpenStack Nova</entry>
      <entry name='version'>13.1.0-1.el7</entry>
      <entry name='serial'>0994820c-3e23-4cc0-9b2c-f34fb88dee4e</entry>
      <entry name='uuid'>d9bda7d7-f68a-45ea-84a1-f50faa44b801</entry>
      <entry name='family'>Virtual Machine</entry>
    </system>
  </sysinfo>
  <os>
    <type arch='x86_64' machine='pc-i440fx-rhel7.2.0'>hvm</type>
    <boot dev='hd'/>
    <smbios mode='sysinfo'/>
  </os>
  <features>
    <acpi/>
    <apic/>
  </features>
  <cpu mode='host-model'>
    <model fallback='allow'/>
    <topology sockets='1' cores='1' threads='1'/>
  </cpu>
  <clock offset='utc'>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='network' device='disk'>
      <driver name='qemu' type='raw' cache='none'/>
      <source protocol='rbd' name='volumes/d9bda7d7-f68a-45ea-84a1-f50faa44b801_disk'>
        <host name='172.23.1.201' port='6789'/>
        <host name='172.23.1.202' port='6789'/>
        <host name='172.23.1.203' port='6789'/>
      </source>
      <backingStore/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </disk>
    <controller type='usb' index='0'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <alias name='virtio-serial0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </controller>
    <interface type='bridge'>
      <mac address='fa:16:3e:54:d9:9f'/>
      <source bridge='qbr74234353-83'/>
      <target dev='tap74234353-83'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>
    <serial type='file'>
      <source path='/var/lib/nova/instances/d9bda7d7-f68a-45ea-84a1-f50faa44b801/console.log'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <serial type='pty'>
      <source path='/dev/pts/4'/>
      <target port='1'/>
      <alias name='serial1'/>
    </serial>
    <console type='file'>
      <source path='/var/lib/nova/instances/d9bda7d7-f68a-45ea-84a1-f50faa44b801/console.log'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <channel type='unix'>
      <source mode='bind' path='/var/lib/libvirt/qemu/org.qemu.guest_agent.0.instance-00000663.sock'/>
      <target type='virtio' name='org.qemu.guest_agent.0' state='connected'/>
      <alias name='channel0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <input type='tablet' bus='usb'>
      <alias name='input0'/>
    </input>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='5901' autoport='yes' listen='0.0.0.0' keymap='en-us'>
      <listen type='address' address='0.0.0.0'/>
    </graphics>
    <video>
      <model type='cirrus' vram='16384' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <stats period='10'/>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </memballoon>
  </devices>
</domain>



chagg at foxmail.com
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