[Moosefs-users] KVM (Kernel Virtual Machine) problems on the native MFS

[Jun C. P. <jun...@gm...>]

Hi,

I have been trying to create a KVM guest VM on the native MFS. But it
has not been quite successful although I getting closer.... Before
delving into the problems, I would like to clarify some relevant
issues. When I used a loop device on top of MFS using sparse files
(For instance, mount -o loop /mnt/mfs/mfs_sparse_200g
/mnt/mfs/loop0/), I didn't have any problems in using KVM on
/mnt/mfs/loop0/).

The problems that I am experiencing now are from the cases where I try
to create KVM guest VMs directly on the native MFS. Here I hope to get
any successful story as to how to **manually** setup a KVM guest OS on
the native MFS without using virt-manager or virt-install because
those tools didn't work on the native MFS.

The following are the details of the problems.

First I made an MFS mountpoint on a KVM node (and MFS client) as follows.
# mfsmount -H $metadata_server_ip -o suid -o dev -o rw -o exec /mnt/mfs
# mount
...
mfs#$metadata_server_ip:9421 on /mnt/mfs type fuse
(rw,allow_other,default_permissions)

Then, create a disk image file for the guest storage.
# qemu-img create -f qcow2 /mnt/mfs/mfskvm1.img 10G
# virt-install --name CentOS5 --ram 1000 --disk
path=/mnt/mfs/mfskvm1.img,size=10 --network network:default
--accelerate --vnc --cdrom /mnt/mfs/CentOS-5.5-x86_64-bin-DVD-1of2.iso
--os-type=linux

Then, I got the following error:

Starting install...
ERROR    internal error unable to start guest: qemu: could not open
disk image /mnt/mfs/mfsvkm1.img

So it seems that the given KVM management tools including virt-install
and virt-manager are not working well directly on the native MFS
because (I guess) there are some incompatible options used by those
tools, which conflicts with MFS.

Then, I tried to manually create a KVM on the naitve MFS as follows
via qemu-kvm.

# /usr/libexec/qemu-kvm -M rhel5.4.0 -m 1024 -smp 1 -name mfskvm1
-uuid af1be3ae-daab-d450-293b-dc03ff7c3c35 -no-kvm-pit-reinjection
-monitor pty -pidfile /var/run/libvirt/qemu/mfskvm1.pid -no-reboot
-boot d -drive file=/mnt/mfs/mfskvm1.img,if=virtio,index=0,format=qcow2,cache=writethrough
-drive file=/mnt/mfs/CentOS-5.5-x86_64-bin-DVD-1of2.iso,if=ide,media=cdrom,index=2,format=raw,cache=writethrough
-net nic,macaddr=12:01:77:99:00:20,vlan=0,model=e1000 -net
tap,fd=33,script=,vlan=0,ifname=vnet0 -serial pty -parallel none -usb
-usbdevice tablet -vnc :10 &

Then, it worked well! The differences from virt-manager or
virt-install are here I use 'cache=writethrough' rather than 'none'
and don't use '-S' as opposed to the options generated by virt-manager
virt-install. So I could successfully installed CentOS.iso on
mfskvm1.img, and then rebooted it, which resulted in the qemu-kvm
process gone due to the option of -no-reboot.

Then, I invoked the qemu-kvm process in order to boot up mfskvm1 using
the installed image on mfskvm1.img as follows:

# /usr/libexec/qemu-kvm -M rhel5.4.0 -m 1024 -smp 1 -name mfskvm1
-uuid af1be3ae-daab-d450-293b-dc03ff7c3c35 -no-kvm-pit-reinjection
-monitor pty -pidfile /var/run/libvirt/qemu/mfskvm1.pid -boot c -drive
file=/mnt/mfs/mfskvm1.img,if=virtio,index=0,boot=on,format=qcow2,cache=writethrough
-drive file=,if=ide,media=cdrom,index=2 -net
nic,macaddr=12:01:77:99:00:20,vlan=0,model=e1000 -net
tap,fd=34,script=,vlan=0,ifname=vnet0 -serial pty -parallel none -usb
-usbdevice tablet -vnc :10 &

Everything works fine except for the problem that the ip determination
for eth0 fails. As I mentioned, when I used virt-install on the MFS
**loop** device, the IP determination worked well, which means my dhcp
server properly responded.

I would like to get some information how to resolve this network setup
issue on the native MFS.

Thanks in advance,

-Jun