[Kimchi-devel] [PATCH] bug fix: setup disks to use cache=none to support live migration.

[Christy Perez]

I also worried about that, but I know that the performance team in the
past said it was okay, as long as you're running a newer OS:

https://ltc3.linux.ibm.com/wiki/LinuxPerformance/KVM-Performance-Tuning

We might want to check with the performance team, unless there's a
specific case which we know will be impacted by cache=none. 

Regards,

Christy


On Thu, 2014-03-06 at 12:23 -0300, Aline Manera wrote:
> On 03/05/2014 11:44 PM, Sheldon wrote:
> > On 03/06/2014 08:46 AM, Royce Lv wrote:
> >> On 2014年03月05日 23:51, Paulo Vital wrote:
> >>> When executing a virsh live migration of a VM created by Kimchi, the
> >>> migration stops due to miss configuration "cache=none" on disk's
> >>> performance parameters.
> >> I'm little worried about make cache 'none' will cause performance 
> >> downgrade for guest in daily running.
> >> Can we allow update this parameter in vm disk edit and change it when 
> >> we decide to live migrate a vm?
> > Agree.
> 
> Patches are welcome! =)
> 
> >>>
> >>> Signed-off-by: Paulo Vital <pvital at linux.vnet.ibm.com>
> >>> ---
> >>>   src/kimchi/vmtemplate.py | 4 ++--
> >>>   1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/src/kimchi/vmtemplate.py b/src/kimchi/vmtemplate.py
> >>> index e2d78a4..89b5e72 100644
> >>> --- a/src/kimchi/vmtemplate.py
> >>> +++ b/src/kimchi/vmtemplate.py
> >>> @@ -152,7 +152,7 @@ class VMTemplate(object):
> >>>               params = {'src': src, 'dev': dev, 'bus': 
> >>> self.info['disk_bus']}
> >>>               ret += """
> >>>               <disk type='file' device='disk'>
> >>> -              <driver name='qemu' type='qcow2'/>
> >>> +              <driver name='qemu' type='qcow2' cache='none'/>
> >>>                 <source file='%(src)s' />
> >>>                 <target dev='%(dev)s' bus='%(bus)s' />
> >>>               </disk>
> >>> @@ -182,7 +182,7 @@ class VMTemplate(object):
> >>>           # Passthrough configuration
> >>>           disk_xml = """
> >>>               <disk type='volume' device='lun'>
> >>> -              <driver name='qemu' type='raw'/>
> >>> +              <driver name='qemu' type='raw' cache='none'/>
> >>>                 <source dev='%(src)s'/>
> >>>                 <target dev='%(dev)s' bus='scsi'/>
> >>>               </disk>"""
> >>
> >> _______________________________________________
> >> Kimchi-devel mailing list
> >> Kimchi-devel at ovirt.org
> >> http://lists.ovirt.org/mailman/listinfo/kimchi-devel
> >
> >
> 
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