Using KVM, its not always working

Yesterda I wrote about using KVM now on 2 servers. Just after I actually wrote that article I discovered KVM wasnt really working on one of these 2 servers (This server was just moved in, and is already a bit older as the other server. Its the old webserver kinda :)).

A first look it shows that everything works ok. However, when I start using it the performance is very bad with IO. After that by looking a bit around the VM was using IDE as driver for the VM. Nothing special, you think? I did actually think the same. Untill I did look at the config file at the other server, and discovered that the other server was using a complete other driver, called virtio for the harddisks at the server. Doing a fast google shows that virtio should provide a far higher performance, so this might be the reason.
After that I tried to actually use virtio at this server as well, but its just erroring out:

qemu: ‘file=/dev/vg0/backup,if=virtio,index=0’ unsupported bus type ‘virtio’

Nothing at google about the error, so no idea badly enough how to fix it. Myself I suppose its caused by this error in dmesg, however I have no idea why:P:

[ 32.705716] kvm: disabled by bios

Currently I don’t have yet a solution for this yet, and iam not sure what to do now. Just using the server without virtualisation? Should work, as its a old box, and only backups and some testing stuff will be on there. Or using xen at it? Both will do it probarly, but I need to think about it first 😛

2 thoughts on “Using KVM, its not always working

  1. The error is because your CPU either doesn’t support VT; or it was not enabled in the bios. KVM will run with our VT but it’s much much slower, and as you’ve found doesn’t support some of the better features like virtio


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