[libvirt-users] Performance tuning questions for mail server

[Alex]

Hi,

>> I made this change by editing the xml, restarting libvirtd, then using
>> virsh to define the xml file and received this message:
>>
>> virsh # define /etc/libvirt/qemu/bwimail02.xml
>> error: Failed to define domain from /etc/libvirt/qemu/bwimail02.xml
>> error: missing source information for device vda
>>
>> Have I done something wrong, or am I missing something?
>
> Will need to see your current XML to tell. But if you simply copied
> and pasted my code, then it's definitely not going to work. For one
> thing, you would need to have created a LVM volume named exactly the
> same way I did.
>
> If you simply changed the paremeters using your existing .img file as
> the source, then it also won't work simply for obvious reasons.

Although I'm not very experienced with libvirt, I'd like to think I
have a reasonable grasp of the technology.

Perhaps I'm showing just how new at this I am, but what would be the
proper way using virsh to change the type to file instead of raw?

I've included my xml below, and would really appreciate any guidance
you may be able to offer. This is the pre-modified version.

One of the things I was working on was trying to get the host
processor spec to mirror that of the guest, but the guest had quite a
few deficiencies from the host, including less cache (4096kb vs
8192kb), and quite a few missing flags on the guest. How does that
impact performance?

This guest config was mostly generated by virt-manager on fedora15.

<domain type='kvm'>
  <name>mail02</name>
  <uuid>ec4f3cf5-2f27-fb3e-72f6-3fa3176b13b6</uuid>
  <memory>4194304</memory>
  <currentMemory>4194304</currentMemory>
  <vcpu>8</vcpu>
  <os>
    <type arch='x86_64' machine='pc-0.14'>hvm</type>
    <boot dev='hd'/>
  </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/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='none'/>
      <source file='/var/lib/libvirt/images/mail02.img'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
function='0x0'/>
    </disk>
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='1' unit='0'/>
    </disk>
    <controller type='ide' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
function='0x1'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:67:2c:4c'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </interface>
    <serial type='pty'>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02'
function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06'
function='0x0'/>
    </memballoon>
  </devices>
</domain>

Thanks,
Alex


>