[Qemu-devel] Qemu-kvm live migration modify

[Qemu-devel] Qemu-kvm live migration modify

[Gilar Dwitresna]

[-- Attachment #1: Type: text/plain, Size: 1449 bytes --]

hi,
I have done make implementation of qemu-kvm instalation for live migration
on ubuntu with sharing storage (NFS) configuration.
the qemu-kvm has been succeed for live migration with default algorithm
(guest without service), but if the guest run the service (streaming
server), the dirty pages rate are increase from 900 to 7000 pages, and live
migration can't succeed.

i have played run live migration with extended downtime 30 second, live
migration can be succees, consequenly the downtime come to increase.
My system use fast ethernet 100mbps for network bandwidth, 2 PC with ram 8
GB for host, 1 PC RAM 4GB HDD 500 GB for NFS shared storage. Guest VM
configure with 2GB RAM HDD 100 GB, migrate from host A to host B.

>From some reference, if the write rate to the memory pages in use by the VM
(here after referred to as the dirty page rate) is high compared with the
cost of transferring the pages between the two hosts involved in the
process, (as dictated, among others, by the network bandwidth,) then live
migration may not be possible.

In the case with the high dirty pages, i run the live migration while the
guest run the streaming server with network bandwidth 100 mbps, then the
server can be migrated.

can i modify qemu-kvm live migration algorithm? and what should i do to
modify this algorithm that can be migrate while the VM Guest run the
servive (streaming server) without extended downtime?

Thanks.
Regards, Papandayan

[-- Attachment #2: Type: text/html, Size: 1662 bytes --]

Re: [Qemu-devel] Qemu-kvm live migration modify

[Thomas Lamprecht]

hi,

this message would probably be better suited on the qemu-discuss list
not the devel.

comments inline.

On 13.04.2016 09:43, Gilar Dwitresna wrote:
> hi, 
> I have done make implementation of qemu-kvm instalation for live
> migration on ubuntu with sharing storage (NFS) configuration.
> the qemu-kvm has been succeed for live migration with default algorithm
> (guest without service), but if the guest run the service (streaming
> server), the dirty pages rate are increase from 900 to 7000 pages, and
> live migration can't succeed.
> 
> i have played run live migration with extended downtime 30 second, live
> migration can be succees, consequenly the downtime come to increase.
> My system use fast ethernet 100mbps for network bandwidth, 2 PC with ram

That's really not fast but more like the lower limit, a guest which
dirties page quickly can saturate the max 100Megabits/s / 8 = 12.5
megabyte/s line really quick. 1 Gb/s (=125 megabyte/s) would be an
better option.

> 8 GB for host, 1 PC RAM 4GB HDD 500 GB for NFS shared storage. Guest VM
> configure with 2GB RAM HDD 100 GB, migrate from host A to host B.
> 
> From some reference, if the write rate to the memory pages in use by the
> VM (here after referred to as the dirty page rate) is high compared with
> the cost of transferring the pages between the two hosts involved in the
> process, (as dictated, among others, by the network bandwidth,) then
> live migration may not be possible.
> 

With qemu 2.5 you have better autoconverge of live migration, see:
http://wiki.qemu.org/Features/AutoconvergeLiveMigration

Also post copy ram (introduced as experimental in qemu 2.5) would be an
option, see http://wiki.qemu.org/Features/PostCopyLiveMigration

cheers,
Thomas

> In the case with the high dirty pages, i run the live migration while
> the guest run the streaming server with network bandwidth 100 mbps, then
> the server can be migrated.
> 
> can i modify qemu-kvm live migration algorithm? and what should i do to
> modify this algorithm that can be migrate while the VM Guest run the
> servive (streaming server) without extended downtime?
> 
> Thanks.
> Regards, Papandayan
>