[Users] Live Migration Optimal execution

[Kir Kolyshkin]

On 11/22/2014 09:09 AM, Nipun Arora wrote:
> Hi All,
>
> I was wondering if anyone can suggest what is the most optimal way to 
> do the following
>
> 1. Can anyone clarify if ploop is the best layout for minimum suspend 
> time during live migration?

Yes (due to ploop copy which only copies the modified blocks).

>
> 2. I tried migrating a ploop device where I increased the --diskspace 
> to 5G,
> and found that the suspend time taken by live migration increased to 
> 57 seconds
> (mainly undump and restore increased)...
> whereas a 2G diskspace was taking 2-3 seconds suspend time... Is this 
> expected?
>

No. Undump and restore times depends mostly on amount of RAM used by a 
container.

Having said that, live migration stages influence each other, although 
it's less so
in the latest vzctl release (I won't go into details here if you allow 
me -- just make sure
you test with vzctl 4.8).


> 3. I tried running a write intensive workload, and found that beyond 
> 100-150Kbps,
> the suspend time during live migration rapidly increased? Is this an 
> expected trend?

Sure. With increased writing speed, the amount of data that needs to be 
copied after CT
is suspended increases.

>
> I am using vzctl 4.7, and ploop 1.11 in centos 6.5

You need to update vzctl and ploop and rerun your tests, there should be
some improvement (in particular with respect to issue #3).

>
> Thanks
> Nipun
>
>
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