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

[Royce Lv]

On 2014年03月08日 04:55, Christy Perez wrote:
> 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
Thanks for your information Christy, pls keep us update.
>
>
> 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>"""
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