Some thought on KVM

Tillotson

I've been playing around with KVM as a test environment for the past while. Mainly
to test apache, samba and backup servers. The computer is core2duo with VT and
2GB of ram. I use virt-manager which is a great piece of software, I had been
messing around with virsh for managing guests but virt-manager just makes the
process so much easier. Virt-manager can be run remotely over ssh, but I had
problems doing this, I suspect it's a firewall issue. The host is centos 5.4 and the
guests are generally ubuntu server.

Right now I'm using a single logical volume for each vm passed to the vm as virtio
disk. I can add additional space by extending the logical volume then booting the vm
with a gparted iso. I've tried qcow2 images but adding additional space seemed
finiky. A pre partitioned logical group resulted in wierdness and poor performance, I
might of been doing something wrong. The only problem I have now is that rsync
uses a lot of CPU when syncing large directories. I've seen this before so I don't
think it is specific to KVM.

I had to configure my own bridge as virt-manager doesn't take care of this. The
default iptables rules on centos block dhcp and dns requests. An iptables script is
available on the centos wiki.

The plan (eventually!!!) is to make the host computer a gateway/firewall for my
network. I'll use either shorewall or just iptables. I'm trying to decide if it would be
better in the long run just to bite the bullet and learn iptables.

The pace of development, especially of the managment tools is quite impressive.
VMware seems to be the defacto standard. Do you think that KVM will be a
serious challenger? Have you used KVM in production and what has been your
experience?

Oh, and merry Christmas everyone

Dorsanty

http://www.xen.org/ eom

Tillotson

I thought Xen was was reaching its end of life.
Redhat's dropping support, KVM made it in the kernel.

Khannie

KVM's been in the kernel for some time. I'm not sure what performance is like for vmware v's KVM now, but I'd definitely be interested in some hardware accelleration (if vmware doesn't already support it). There are other virtualisation options out there (virtualbox for example) but I haven't used them.

As for using them in production...haven't done it yet. I've used virtual machines for testing and I know our company uses them for support purposes (we'd replicate a customer environment but leave the vm powered off unless there's an issue). I also use one for maintaining internet access on the host machine while VPNing on the guest.

Tillotson

Got shorewall installed on the host. Network now looks like this:

Internet--->Smart BB Router--->Centos(KVM, Shorewall)--->Virtual Bridge--<
--->vm(Backuppc)
--->vm(Samba,Sabnzbd,etc)
--->BT Router(DHCP)--->Wireless Net

If anyone's interested in configs I'll post them. I'll probably add another virtual bridge
and configure a dmz for hosting apache, also a squid proxy on centos might be nice.
I'm done for a while though

djmarkus

Tillotson wrote: »

I thought Xen was was reaching its end of life.
Redhat's dropping support, KVM made it in the kernel.

Its a long way off EOL. Citrix is making a good go of XenServer as a commercial product and Dom0 support will be in the kernel in the next few releases.

And anyway IO wise KVM sucks compared to Xen, this is mostly because KVM pushes nearly all IO through userspace(qemu), this is what's sucking up all your CPU with doing an rsync.

croo

Tillotson wrote: »

I'm trying to decide if it would be
better in the long run just to bite the bullet and learn iptables.

If you do decide to go the iptables route, I can recommend Ziegler's "Linux Firewalls"
for everything you need to know. Not having a strong networking background I I found it very enlightening, and didn;t need any other resources to know all I needed to about iptables.
http://www.amazon.com/Linux-Firewalls-Landmark-Robert-Ziegler/dp/0735710996