Farkas Levente wrote: > hi, > in the last 2 weeks we play a lot with our new server which we but to a > our virtual server for the development and collect some very subjective > experience. we use kvm and virt-manager, but sometimes i'm not really > sure about the whether it's kvm or virt-manager problem so i collect > them together. our system: > thansk! > MB: Intel S3000AHV > CPU: Intel Core 2 Quad CPU Q6600 @ 2.40GHz > RAM: 8GB > CentOS 5 x86-64 host system with: > kernel-2.6.18-8.1.8.el5 > kmod-kvm-35-1.2.6.18_8.1.8.el5 > kvm-35-1 > libvirt-0.3.2-2 > libvirt-python-0.3.2-2 > python-virtinst-0.300.0-1 > virt-manager-0.5.0-1 > virt-top-0.3.2.5-1 > virt-viewer-0.0.2-1 > > 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. > this issue is known and will be fix soon. > 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 from version 36 support above 2giga of ram (it was tested with 32giga ram guest) > 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. > > 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. > > thanks for all this information, this exactly what we need!