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Can OpenVZ run under KVM? Virtualization within Virtualization
I have a main server running OpenVZ kernel hosting a few critical website with db and likes, i did daily backup of the whole OpenVZ container to another VPS server. Question is, if anything were to happen to my main server (server crash, ISP issue, etc), i need the backup container to be up within the next hour or so. Provisioning another server will not be an option since it takes 3-7 days depending on ISP, therefore i was thinking:
Can a KVM container be loaded with OpenVZ kernel? If yes, then how can i do it? so that i could just load the OpenVZ container backup into the KVM running OpenVZ kernel (with extra IP), change DNS and up with minimum downtime.
Input is appreciated.
Comments
Yes. Just install it with the standard OpenVZ installation method.
yes it can, but you may see some loss in performance.
@Mun, some performance loss will not be an issue. Those website are critical in a way uptime is important but does not use extensive processing power or memory.
@Rallias, just the normal OpenVZ installation will do? no restriction or anything on the KVM which would prevent OpenVZ kernel be installed on it?
As far as I'm aware, Digital Ocean is the only provider that restricts what kernels can be used on their KVM VPS's.
The performance loss will be sizeable for ovz inside kvm comparing with bare metal ovz. I would estimate some 10% at least, if done really well.
Honestly, you can probably get it down to about 5%, using noop IO scheduler on VM, using mapped block devices (lvm full provision), low nonsense on the host node.
@dobuz Do as @Rallis said.
+ The performance drop in the KVM from bare metal may be 10% but the drop in performance between the KVM and the openVZ containers inside the KVM is negligible. Add "elevator=noop" to /etc/grub.conf.
I do this a lot for similar reasons. It works without issues for me.
EDIT: You can PM me if you get hung up anywhere ...