Re: Using CentOS-6.x on KVM-hosts - what are the threats?

[ilya]

Vladimir

It comes down to version of qemu and cpu flags. As you know this is not
related to cloudstack.

Because of major differences in qemu and cpu flags -  safest method is
power down and power up.

QEMUs claim to fame was that it can migrate from AMD to Intel and vice
versa. In practice its hit or miss.

What is guest.cpu.mode set to in your agent.properties?

Also, this maybe a good help for "guest.cpu.mode" capabilities.

https://libvirt.org/formatdomain.html#elementsCPU

Regards
ilya

On 2/25/17 2:29 AM, Vladimir Melnik wrote:
> Thank you for the comment, Simon! The most funny thing is that I've added 3
> new hosts to my infrastructure in December, their hardware is awesome, so
> their hardware refresh is not a matter of the nearest future. :) Anyhow, 6.x
> works great and the only thing I regret is lacking certain features (such as
> IOpS limits).
> 
>  
> 
> I'm also maintaining a cluster of 5 hosts (primary storages aren't local,
> they're connected via GlusterFS & NFS) which've been running 6.x too. I've
> upgraded 3 of hosts from 6.x to 7.x, but when I'm trying to migrate a VM
> from the "old" hosts to the "new" ones, the migration is being timed out and
> the VM is being frozen in the "paused" state. I noticed a difference in the
> CPU-flags set: all the hosts running 7.x have the "nopl" flag, but the hosts
> running 6.x don't. This option appears only after installing 7.x and maybe
> this is the cause. Does anyone have any suggestions on the reason that
> causes freezing the VMs when they've been migrating from the 6.x-powered
> hosts to the 7.x-powered ones? Is that the "nopl" flag? Is that anything
> else? Thanks to all!
> 
> 

Re: Using CentOS-6.x on KVM-hosts - what are the threats?

[Vladimir Melnik]

Thank you for the comment, Simon! The most funny thing is that I've added 3
new hosts to my infrastructure in December, their hardware is awesome, so
their hardware refresh is not a matter of the nearest future. :) Anyhow, 6.x
works great and the only thing I regret is lacking certain features (such as
IOpS limits).

 

I'm also maintaining a cluster of 5 hosts (primary storages aren't local,
they're connected via GlusterFS & NFS) which've been running 6.x too. I've
upgraded 3 of hosts from 6.x to 7.x, but when I'm trying to migrate a VM
from the "old" hosts to the "new" ones, the migration is being timed out and
the VM is being frozen in the "paused" state. I noticed a difference in the
CPU-flags set: all the hosts running 7.x have the "nopl" flag, but the hosts
running 6.x don't. This option appears only after installing 7.x and maybe
this is the cause. Does anyone have any suggestions on the reason that
causes freezing the VMs when they've been migrating from the 6.x-powered
hosts to the 7.x-powered ones? Is that the "nopl" flag? Is that anything
else? Thanks to all!

Re: Using CentOS-6.x on KVM-hosts - what are the threats?

[Nux!]

This might still be an issue

http://www.nux.ro/oldblog/archive/2014/01/Taking_KVM_volume_snapshots_with_Cloudstack_4_2_on_CentOS_6_5.html

--
Sent from the Delta quadrant using Borg technology!

Nux!
www.nux.ro

- Original Message -
> From: "Vladimir Melnik" 
> To: "users" 
> Sent: Friday, 17 February, 2017 18:53:14
> Subject: Using CentOS-6.x on KVM-hosts - what are the threats?

> Dear colleagues,
> 
> I've just realized that my KVM-hosts are running CentOS-6 whilst it's
> recommended to use CentOS-7 with the new versions of ACS. Everything
> seems to be fine (some of these hosts are working for a few years),
> hosts are working and things are great, but I'd like to ask a couple of
> questions. Here they are.
> 
> (1) How high is the chance of the next version of ACS (4.10 or 4.11)
> will be incompatible with CentOS-6? Should I worry about that and
> consider upgrading to CentOS-7 immediately?
> 
> (2) What ACS features I'm missing because of that? I suppose that I'll
> be disappointed if I try to limit a VM's IO-consumption, just because
> old good QEMU-0.9 won't support it. Am I right? Are there other things
> that are worth of upgraging to CentOS-7?
> 
> Thank you very much in advance for your replies!
> 
> --
> V.Melnik

Re: Using CentOS-6.x on KVM-hosts - what are the threats?

[Simon Weller]

Vladimir,


To answer your immediate question, I don't think you're at major risk by 
staying on Centos 6 in the medium term. Centos 6 will be supported by Centos 
until Nov 30th, 2020. In terms of what ACS will support, I don't think it has 
been discussed on the list for a while. There will be a point at which it won't 
make sense based on the the lack of features available and personally I think 
we might be starting to get close. As of 4.9, we now have a LTS release out and 
that most likely will be the release most Centos 6 users will stay on.


We have been running Centos 7 hosts now for a while and it's a lot more stable 
in our opinion and just works out of the box, especially with storage backends 
such as Ceph.

If you've been running Centos 6 for a few years,  you might be be getting close 
to a hardware refresh anyway. If you are, you could build a new Centos 7 based 
cluster and them migrate primary storage to a new cluster.

- Si


From: Vladimir Melnik 
Sent: Friday, February 17, 2017 12:53 PM
To: users@cloudstack.apache.org
Subject: Using CentOS-6.x on KVM-hosts - what are the threats?

Dear colleagues,

I've just realized that my KVM-hosts are running CentOS-6 whilst it's
recommended to use CentOS-7 with the new versions of ACS. Everything
seems to be fine (some of these hosts are working for a few years),
hosts are working and things are great, but I'd like to ask a couple of
questions. Here they are.

(1) How high is the chance of the next version of ACS (4.10 or 4.11)
will be incompatible with CentOS-6? Should I worry about that and
consider upgrading to CentOS-7 immediately?

(2) What ACS features I'm missing because of that? I suppose that I'll
be disappointed if I try to limit a VM's IO-consumption, just because
old good QEMU-0.9 won't support it. Am I right? Are there other things
that are worth of upgraging to CentOS-7?

Thank you very much in advance for your replies!

--
V.Melnik