Hi EJ and Wei,

First of all, I don't think there is a strong relation between bare-metal and live-migration.

In Kubernetes, once a Pod is assigned to a node, it won't go anywhere else in its entire life. And the pod itself should be stateless and
even stateful workload should rely on permanent volumes or other global resources. Under the above assumption, any migration-like
requirements should be defined by deployment or other high-level tasks definition instead of sandbox-level migration. This is the philosophy
of Kubernetes.

However, I understand Wei, who is at the role of an operator just like me, he may be very happy if he could be able to do some tweak to
avoid unnecessary re-schedule operations, which will reduce service interruption at least. The only problem here is how much is the cost
of the live migration.

Personally, I don't think I need live migration in the current stage but I won't reject the live-migration feature if it does not have significant side effects.

-Xu


On Tue, Dec 18, 2018 at 3:30 PM zhangwei (CR) <zhangwei555@huawei.com> wrote:

 

Hi EJ,

 

Kata Container is one tiny VM per POD, you can choose to run k8s+kata in another VM provisioned by OpenStack, in this case, we run into the nested virtualization scenario. It works well but brings some unnecessary overhead from nested VM usage.

 

To avoid this kind of overhead, we can also choose to run K8S cluster on bare metal, which means every worker/node of K8S is bare metal machine instead of VM. By doing this, K8S becomes the lowest level of infrastructure and should provide live migration capability similar to OpenStack VM scenarios.

 

Live migration could be useful in this scene as every POD is a VM running on bare metal now, we need a reliable way to keep workload alive when host machine needs reboot(let’s say, fixing some CVEs).

 

-Wei

 

发件人: EJ Campbell [mailto:ejc3@oath.com]
发送时间: 2018年12月18日 14:11
收件人: zhangwei (CR) <zhangwei555@huawei.com>
抄送: Ernst, Eric <eric.ernst@intel.com>; Stefan Hajnoczi <stefanha@redhat.com>; sweil@redhat.com; Qixuan Wu <qixuan.wu@linux.alibaba.com>; Graham Whaley <graham.whaley@gmail.com>; miklos@szeredi.hu; kata-dev@lists.katacontainers.io; swhiteho@redhat.com; vgoyal@redhat.com
主题: Re: [kata-dev] 答复: [Announce] virtio-fs released with Kata Containers support

 

Hi Zhangwei,

 

Could you go into more detail on the use case for live migration on bare metal?

 

Thanks,

EJ

 

 

On Mon, Dec 17, 2018 at 6:20 PM zhangwei (CR) <zhangwei555@huawei.com> wrote:

Stefan, Eric,

There isn't live migration requirement so far, but, I will take this as a potential requirement when Kata is growing more powerful.
In my mind, this is rational as some of us are running kata on bare metal, in this scene, we don't have an infrastructure software such as OpenStack to guarantee the lifecycle of workload.

Virtio-fs is in RFC state, it could be OK as long as it doesn't have native gap for supporting live migration,  and I will be glad to see it being listed in some roadmap.

By the way, really nice work! We finally get a better option against 9pfs :-) Thanks!

-----邮件原件-----
发件人: Ernst, Eric [mailto:eric.ernst@intel.com]
发送时间: 2018年12月17日 22:30
收件人: Stefan Hajnoczi <stefanha@redhat.com>
抄送: sweil@redhat.com; Qixuan Wu <qixuan.wu@linux.alibaba.com>; Graham Whaley <graham.whaley@gmail.com>; miklos@szeredi.hu; kata-dev@lists.katacontainers.io; swhiteho@redhat.com; vgoyal@redhat.com
主题: Re: [kata-dev] [Announce] virtio-fs released with Kata Containers support

Stefan -

No, there isn’t a live migration requirement for Kata (sorry for the top post).

Eric

> On Dec 17, 2018, at 6:27 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
>> On Sun, Dec 16, 2018 at 09:09:48AM +0800, Qixuan Wu wrote:
>> 1) Did you compare the performance to the virtio-blk raw or qcow2
>> solution of normal virtual machine?
>
> Not yet.
>
> Guest and host page cache performance can dominate benchmarks, so we
> typically use fio direct=1 with QEMU -drive cache=none (O_DIRECT) to
> focus purely on disk I/O performance and not page cache.  The same
> thing can be done with virtio-fs so that every I/O operation requires
> communication with the host.  In theory virtio-fs should be comparable
> to virtio-blk on raw.
>
> In real-world scenarios the page cache will be enabled, especially for
> the virtio-fs DAX feature.  So I need to think carefully about what to
> benchmark, but it will probably include both configurations.
>
>> 2) Whether does it impact live-migration of guest os ?
>
> Virtio-fs currently does not support live migration.  Is there a
> requirement for live migration with Kata Containers use cases?
>
> Stefan

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Xu Wang
CTO & Cofounder, Hyper
github/twitter/wechat: @gnawux
http://hyper.sh

Hyper_: Make VM run like container