[libvirt-users] Performance tuning questions for mail server

Robin Lee Powell rlpowell at digitalkingdom.org
Mon Oct 10 02:20:39 UTC 2011


On Sun, Oct 09, 2011 at 03:26:52PM -0400, Alex wrote:
> 
> >>     <disk type='file' device='disk'>
> >>       <driver name='qemu' type='raw'/>
> >>       <source file='/var/lib/libvirt/images/mail02.img'/>
> >>       <target dev='vda' bus='virtio'/>
> >>       <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
> >> function='0x0'/>
> >
> > I meant raw disk devices rather than files e.g.
> > <disk type='block' device='disk'>
> >      <driver name='qemu' type='raw' cache='none'/>
> >      <source dev='/dev/server02_vg1_2tb/lv_vm03_swap'/>
> >      <target dev='vdb' bus='virtio'/>
> > </disk>
> >
> > This eliminates one layer of filesystem overheads.
> 
> Can this type change be done without modifying the image, or must
> some conversion be done prior to making this change?

You can do that at any time; it just requires a reboot.  You really
want caching off; see
http://publib.boulder.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=%2Fliaat%2Fliaattunkickoff.htm

-Robin




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