Re: [Qemu-devel] qemu disk use writeback don't take effect in centos 7.2 1511

[Paul Schlacter]

Hi David:
     yes, with the same qemu,  centos 7.2 guest cache is writeback and
none, the disk io almost, writeback feeling no effect.
      but 7.1/7.3/7.4  cache is writeback was significantly faster than
none model

On Wed, Nov 1, 2017 at 8:02 PM, Paul Schlacter <address@hidden> wrote:

> Hi David:
>      yes, with the same qemu,  centos 7.2 guest cache is writeback and
> none, the disk io almost, writeback feeling no effect.
>       but 7.1/7.3/7.4  cache is writeback was significantly faster than
> none model
>
> On Wed, Nov 1, 2017 at 5:45 PM, Dr. David Alan Gilbert <
> address@hidden> wrote:
>
>> * Paul Schlacter (address@hidden) wrote:
>> > qemu version:  2.9.0
>> > image: centos 7.2 1511 raw
>> > cache mode: writeback
>> >
>> >
>> > In centos7.2 time, the use of writeback and none, the result of dd disk
>> is
>> > the same io, no change
>> >
>> > But I replaced centos7.1 centos7.3 centos7.4 when writeback was
>> > significantly faster than none
>> >
>> > Would like to ask what is going on, how to solve ?
>>
>> Hi Paul,
>>   Can you just clarify your setup please;  do you mean that
>> with the same qemu setup but a 7.2 guest rather than a 7.1/7.3 guest
>> the behaviour changes?
>>
>> Dave
>>
>> --
>> Dr. David Alan Gilbert / address@hidden / Manchester, UK
>>
>
>