[CentOS-virt] Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage

Anthony Liguori anthony at codemonkey.ws
Sat Sep 8 15:18:49 UTC 2007

On Sat, 2007-09-08 at 13:15 +0200, Farkas Levente wrote:
> hi,
> kvm is not ready for production use for many reason:
> it can't reboot which imho a very basic feature, what's more can't even
> shutdown/poweroff. the centos i386 guest are not able to shutdown on the
> x86_64 host (strange the x86_64 centos and the i586 mandrake-9 are able
> to shutdown) or what's seems to be more likely it's a random think.
> can't give 2GB ram to any guests not even 2, but 1.9999 is ok. what's
> more i've to discover this in the hard way virt-manager gives some
> strange error message (anyway none of the virt-manager's error message
> are useful, just strange stack trace without any kind of useful info).

kvm-36 now supports more than 2GB of RAM per guest.  You're one version
off for that.

> the host see as i've 4 cpu. i've got a change to gives more cpu to the
> guest, what's more they starts, but after a few minutes running the
> system crash. not just the guest os but the host os crash without any
> kind of info, log or any useful info what was the cause of it, but hard
> reset helps:-((( first of all it's serious problem, even if it's a known
> bug and documented somewhere (but there is not any kind of docs about
> neither kvm nor virt-manager/libvirt and what i can find that very
> limited), since all of the new hvm cpu (which is required for kvm) has
> more core, so the guest can't use the real power of the cpu this means
> i've to put a lots of guests with one virtual cpu to the host or
> currently can't exploit these cpus.

I'm having difficulty understanding what your problem is.  Are you
saying that guest SMP isn't working for you?  The host OS definitely
shouldn't crash.  Can you be more specific about what configs you are
using?  There was a host oops fixed in kvm-36 so upgrading may help you.


Anthony Liguori

> libvirt not start the guest when the host started, not saved the state
> of the guests when stopped, when restarted all guest get into shutdown
> state. may be it's just libvirt but, but if kvm not able to save it's
> guest's state that it's a real pain. this behavior not acceptable in a
> real environment.
> in virt-manager can't modify virtual cpu number of the guests
> (virt-manager crash with another unusable stacks trace). it i modify the
> xml config file by hand i've to restart libvirt in order to read it.
> even if i just modify one guest's config, but as if i restart libvirtd
> the all other guest will be killed it's another nice feature.
> from vit-manager i can't assign swap partitions (and any other device
> to the guests) during guest creation. i precreate lvm partition on the
> host for root and swap to all of our guests (about 10) but it's a real
> pain to reload libvirtd (which kills all guests) to add a new disk to
> the guest which can be used as a swap or other partition. what's more
> it'd be useful to add swap partition during install. the same thing
> apply to cdrom too.
> if i made a mistake in the libvirtd xml config file, then i don't get
> any kind of error message just libvirt don't start the given guest. no
> error message service seems to start without error and don't know what
> was the reason that the guest not start (sometimes because syntactic
> error in the config file, sometimes kvm/qemu not support it eg more then
> 2gb mem). there are unwritten unix/linux tradition eg if there are error
> during a service startup report it some log file. if a service can't
> start without error then it not start at all eg. if i've apache with 5
> virtual host but one of it's config has error then the whole httpd not
> started. it'd have to be the same with libvirt too.
> libvirt config file has all the features as qemu command line (if not it
> can't be used by advanced users)? but i don't know since there is not a
> reference docs for the config file.
> there is not a detailed reference docs about libvirtd config (and at the
> same time the gui not contains all the settings). for the the xml format
> is a bit redundant eg. "source dev", "target dev" why not just source
> and target, inside interface type='bridge' 'source bridge' why not just
> source (i've to modify two place when i'd like to switch from network to
> bride. ok these are just small cosmetic thing just mention.
> when create a new guest in virt-manager and reach the last page and
> press finish then most of the time (2 times from 3) i've got an error
> something like "can't connect to qemu" after i press ok and press again
> finish then it's able to create the new host (so always have to retry it).
> in virt-manager when a guest is shutdown and double-click on the guest
> and try to start it it's not possible. you've to select the guest in the
> main windows, right-click and start it.
> the new vnc based console is very unstable or just virt-manager not able
> to connect it. many times i double click on a guest in virt-manager i
> got the window can't connect to console while the guest are running.
> that's why i like to see again the serial console.
> we've got other virtual servers with xen and openvz, with has other
> problems but works. my conclusion is that currently kvm, libvirtd,
> virt-manager (et-mgmt-tools) seems very promising. but currently just in
> a very alpha stage using even in non mission critical but production
> environment still a very 'brave' decision. xen has a few years vantage,
> but it's at least usable in real environment.
> i'm on the these list and see what kind of problem you're working which
> is great but at the same it'd be useful to fix the most basic problems
> with these tools.
> just my 2c to these community.

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