[ovirt-users] Slow conversion from VMware in 4.1

[Luca 'remix_tj' Lorenzetto]

On Tue, Feb 6, 2018 at 11:19 AM, Richard W.M. Jones <rjones at redhat.com> wrote:
> On Tue, Feb 06, 2018 at 11:11:37AM +0100, Luca 'remix_tj' Lorenzetto wrote:
>> Il 6 feb 2018 10:52 AM, "Yaniv Kaul" <ykaul at redhat.com> ha scritto:
>>
>>
>> I assume its network interfaces are also a bottleneck as well. Certainly if
>> they are 1g.
>> Y.
>>
>>
>> That's not the case, vcenter uses 10g and also all the involved hosts.
>>
>> We first supposed the culprit was network, but investigations has cleared
>> its position. Network usage is under 40% with 4 ongoing migrations.
>
> The problem is two-fold and is common to all vCenter transformations:
>
> (1) A single https connection is used and each block of data that is
> requested is processed serially.
>
> (2) vCenter has to forward each request to the ESXi hypervisor.
>
> (1) + (2) => most time is spent waiting on the lengthy round trips for
> each requested block of data.
>
> This is why overlapping multiple parallel conversions works and
> (although each conversion is just as slow) improves throughput,
> because you're filling in the long idle gaps by serving other
> conversions.
>
[cut]

FYI it was a cpu utilization issue. Now that vcenter has a lower
average cpu usage, migration times halved and returned back to the
original estimations.

Thank Richard for the infos about virt-v2v, we improved our knowledge
on this tool :-)

Luca

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Luca 'remix_tj' Lorenzetto, http://www.remixtj.net , <lorenzetto.luca at gmail.com>