Open Stack

Hi Xu,

I mentioned the bare metal because if you run kata-containers in another VM provided by OpenStack, you can do live-migration to the whole VM(host for kata), and bypass kata live-migration requirement.

> 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.

I agree with you as a technical guy, this philosophy simplifies things a lot and I love simplicity. But life is not always easy, when users/customers pay enough money, the marketing guy will force me to  do anything customers want, in general, I will choose to argue --> fail --> then add the new feature, or simply find a new job ☺

Permanent volumes sounds good for stateful workload, but not all workloads are containerized perfectly. When drain the node or respawn the POD in another node, you still lost some(number changes according to how frequently the workload write the persist volume) calculation/data. Another use case is the workload start very slowly and they want to avoid restarting.

I’ll suggest users only run stateless workload in K8s cluster, but this isn’t achievable.  Some people are evening running systemd+sshd in a container which is worse.

-Wei

发件人: Xu Wang [mailto:xu at hyper.sh]
发送时间: 2018年12月18日 16:02
收件人: zhangwei (CR) <zhangwei555 at huawei.com>
抄送: EJ Campbell <ejc3 at oath.com>; kata-dev at lists.katacontainers.io
主题: Re: [kata-dev] 答复: 答复: [Announce] virtio-fs released with Kata Containers support

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 at huawei.com<mailto:zhangwei555 at 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 at oath.com]
发送时间: 2018年12月18日 14:11
收件人: zhangwei (CR) <zhangwei555 at huawei.com<mailto:zhangwei555 at huawei.com>>
抄送: Ernst, Eric <eric.ernst at intel.com<mailto:eric.ernst at intel.com>>; Stefan Hajnoczi <stefanha at redhat.com<mailto:stefanha at redhat.com>>; sweil at redhat.com<mailto:sweil at redhat.com>; Qixuan Wu <qixuan.wu at linux.alibaba.com<mailto:qixuan.wu at linux.alibaba.com>>; Graham Whaley <graham.whaley at gmail.com<mailto:graham.whaley at gmail.com>>; miklos at szeredi.hu<mailto:miklos at szeredi.hu>; kata-dev at lists.katacontainers.io<mailto:kata-dev at lists.katacontainers.io>; swhiteho at redhat.com<mailto:swhiteho at redhat.com>; vgoyal at redhat.com<mailto:vgoyal at 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 at huawei.com<mailto:zhangwei555 at 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 at intel.com<mailto:eric.ernst at intel.com>]
发送时间: 2018年12月17日 22:30
收件人: Stefan Hajnoczi <stefanha at redhat.com<mailto:stefanha at redhat.com>>
抄送: sweil at redhat.com<mailto:sweil at redhat.com>; Qixuan Wu <qixuan.wu at linux.alibaba.com<mailto:qixuan.wu at linux.alibaba.com>>; Graham Whaley <graham.whaley at gmail.com<mailto:graham.whaley at gmail.com>>; miklos at szeredi.hu<mailto:miklos at szeredi.hu>; kata-dev at lists.katacontainers.io<mailto:kata-dev at lists.katacontainers.io>; swhiteho at redhat.com<mailto:swhiteho at redhat.com>; vgoyal at redhat.com<mailto:vgoyal at 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 at redhat.com<mailto:stefanha at 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<http://hyper.sh/>

Hyper_: Make VM run like container
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