qemu not supporting live snapshots

[Norbert78]

Hi forum,
I'm a somehow experienced Debian user and new to CentOS. I'm managing a small HP server and somebody said that CentOS would be the better OS for this
I'm mainly using this server to run a couple of VMs using KVM/QEMU. Now, i'm trying to establish some backup concept but getting to the limits as I'm constantly getting an error message when trying to create a live image. The error message basically says that live snapshots are not supported by this version of qemu that I'm using.
I googled around a bit and it seems that this is a known problem and that the QEMU Version from the yum repos for CentOS does simply not contain this feature. I have no idea, why but this seems to be the situation.
Some posts suggest that I should replace my kvm-qemu package by the kvm-qemu-rhel package but there is not guidance on how to do this.
I'm really confused a bit. Is this a commmon thing under CentOS that the software is kind of castrated?

Coming to my main question: Is there a good way to install the RHEL packages under CentOS? Or will I have to live with this situation?

Thanks for your advice in advance
Norbert

[TrevorH]

CentOS is identical to RHEL except for branding - all mentions of Redhat and RH logos are removed and everything is rebuilt. If you find a difference that isn't branding or logos then feel free to raise a bug on bugs.centos.org. However, qemu* packages are identical between the 2 and the same restrictions that are in the CentOS versions should also be in the RHEL versions.

What are the exact commands you run and what are the exact error messages that you receive? What is the output from uname -a and from rpm -qa qemu\* libvirt\* ?

[hunter86_bg]

Here is a short description of the difference between the "qemu-kvm" and the "qemu-kvm-rhev" as per the following solution:

Currently, some major features offered by qemu-kvm-rhev but not offered by qemu-kvm are:

Live snapshots and related tasks (e.g.: Live Storage Migration) (Admin. Guide)
Streaming, mirroring and live-merge (e.g.: Block-jobs, Live snapshot delete) (Technical Reference Guide)
I/O throttling via qemu (Storage quality of service in RHV)
I/O Threads (VM Management Guide)
Memory hotunplug (ACPI based)
Memory hotplug (ACPI based)
Support for Windows guests (Certified guest OS on RHEL with KVM, Certified guest OS on RHV/OSP)
Several Machine types missing (Certified guest OS on RHEL with KVM, Certified guest OS on RHV/OSP)
vhost-user (QEMU documentation)
CPU hotunplug
Scaling up to 288 vCPUs (KVM limits, RHV limits)
NUMA guest locality for PCIe

Installing the qemu-kvm-rhev package outside of a RHV or Red Hat Openstack Platform environment is not supported.

Though I'm not sure which repo provides the following packages. I see the "qemu-kvm-ev" package , which should be the CentOS version of the RedHat's "qemu-kvm-rhev" package.

[Norbert78]

Now I'm getting even more confused.
Based on the answer of TrevorH I was actually hoping that I simply did not install the right packet. When I installed CentOS it was my understanding as well that it would be identical to the RHEL.
However, looking at the answer from hunter86_bg is exactly I'm experiencing. A very important feature is simply not existing in the CentOS QEMU version. I mean: Who wants to shutdown a VM to take a snapshot

The command that triggers the error is:

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virsh snapshot-create-as ${vm} backup --disk-only --atomic --no-metadata --quiesce 2>&1

The packet qemu-kvm-ev is not found on my system. And currently, I'm wondering whether it would be a good idea to install it. Are there any trustworthy sources where I could get this packet from?

Any thoughts on that would be highly appreciated.

Thanks
Norbert


BTW:

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uname - says: Linux server 3.10.0-693.11.1.el7.x86_64 #1 SMP Mon Dec 4 23:52:40 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
and rpm -qa qemu\* libvirt\* says:
libvirt-glib-1.0.0-1.el7.x86_64
libvirt-libs-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-network-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-lxc-3.2.0-14.el7_4.5.x86_64
libvirt-client-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-iscsi-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-mpath-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-3.2.0-14.el7_4.5.x86_64
libvirt-3.2.0-14.el7_4.5.x86_64
libvirt-python-3.2.0-3.el7_4.1.x86_64
qemu-img-1.5.3-141.el7_4.4.x86_64
libvirt-daemon-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-nwfilter-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-config-network-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-interface-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-core-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-scsi-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-logical-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-qemu-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-rbd-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-nodedev-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-config-nwfilter-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-secret-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-disk-3.2.0-14.el7_4.5.x86_64
libvirt-daemon-driver-storage-gluster-3.2.0-14.el7_4.5.x86_64
qemu-kvm-common-1.5.3-141.el7_4.4.x86_64
qemu-kvm-1.5.3-141.el7_4.4.x86_64

[TrevorH]

What you're missing is that RHEV is not RHEL. CentOS is a clone of RHEL which has virtualization packages provided for it. However the product that RH sell for virtualization is RHEV and that contains different sets of packages with different things enabled/disabled.

CentOS itself does not ship the qemu-kvm-ev package that you're looking for but one of the CentOS SIGs does do so. I'm not sure which SIG it is but run yum list centos-release\* and you'll see a list of all the release files for all the CentOS SIGs. Oddly enough I think it will be

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centos-release-qemu-ev.noarch                                    1.0-2.el7                              extras

[Norbert78]

Thanks for this clarification. I will give it a try tomorrow.
Do you think that I will have to remove/remove the other QEMU package before installing the -ev version?
Norbert

[moricio]

Hello!

Did you succeed in the live snapshots EV test? If so, can you please give me directions on how to achieve it? Thanks!


MRamirez

[TrevorH]

yum install centos-release-qemu-ev
yum install qemu-kvm-ev

You may need to remove the current qemu-kvm package first, not sure if they can coexist.

[hunter86_bg]

They don't coexist in RHEL and the 'ev' package is treated as an upgrade, so I expect the same behaviour on CentOS.

[moricio]

Hi.

I want to report that this worked PERFECTLY. It replaced the installed version.

Thanks!

Moricio

yum install centos-release-qemu-ev
yum install qemu-kvm-ev

You may need to remove the current qemu-kvm package first, not sure if they can coexist.