I confirm that without 'cache' option, I have got from iostat those result while doing 'savevm'
Device: sda rrqm/s: 0.00 wrqm/s: 316.00 r/s: 0.00 w/s: 94.80 rkB/s: 0.00 wkB/s: 1541.60 avgrq-sz: 32.52 avgqu-sz: 0.98 await: 10.32 svctm: 10.10 %util: 95.76 I also confirm, that when option 'cache=unsafe' is used, snapshot (from qemu monitor) is done as quickly as it should (few seconds). I am not sure if this is a solution or workaround or just a closer description of a bug. http://libvirt.org/formatdomain.html#elementsDisks describes option 'cache'. When I use that (cache="none") it spits out: error: Failed to create domain from vm.xml error: internal error process exited while connecting to monitor: kvm: -drive file=/home/dum8d0g/vms/deb.qcow2,if=none,id=drive-ide0-0-0,boot=on,format=qcow2,cache=none: could not open disk image /home/dum8d0g/vms/deb.qcow2: Invalid argument When that option is removed, domain is created successfuly. I guess I have another bugreport to fill. So, for me, the issue is somehow solved from the qemu side. I think, this could be marked as wontfix. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) Status in QEMU: New Status in “qemu-kvm” package in Ubuntu: Confirmed Bug description: Action ====== # time virsh snapshot-create 1 * Taking snapshot of a running KVM virtual machine Result ====== Domain snapshot 1300983161 created real 4m46.994s user 0m0.000s sys 0m0.010s Expected result =============== * Snapshot taken after few seconds instead of minutes. Environment =========== * Ubuntu Natty Narwhal upgraded from Lucid and Meerkat, fully updated. * Stock natty packages of libvirt and qemu installed (libvirt-bin 0.8.8-1ubuntu5; libvirt0 0.8.8-1ubuntu5; qemu-common 0.14.0+noroms- 0ubuntu3; qemu-kvm 0.14.0+noroms-0ubuntu3). * Virtual machine disk format is qcow2 (debian 5 installed) image: /storage/debian.qcow2 file format: qcow2 virtual size: 10G (10737418240 bytes) disk size: 1.2G cluster_size: 65536 Snapshot list: ID TAG VM SIZE DATE VM CLOCK 1 snap01 48M 2011-03-24 09:46:33 00:00:58.899 2 1300979368 58M 2011-03-24 11:09:28 00:01:03.589 3 1300983161 57M 2011-03-24 12:12:41 00:00:51.905 * qcow2 disk is stored on ext4 filesystem, without RAID or LVM or any special setup. * running guest VM takes about 40M RAM from inside, from outside 576M are given to that machine * host has fast dual-core pentium cpu with virtualization support, around 8G of RAM and 7200rpm harddrive (dd from urandom to file gives about 20M/s) * running processes: sshd, atd (empty), crond (empty), libvirtd, tmux, bash, rsyslogd, upstart-socket-bridge, udevd, dnsmasq, iotop (python) * networking is done by bridging and bonding Detail description ================== * Under root, command 'virsh create-snapshot 1' is issued on booted and running KVM machine with debian inside. * After about four minutes, the process is done. * 'iotop' shows two 'kvm' processes reading/writing to disk. First one has IO around 1500 K/s, second one has around 400 K/s. That takes about three minutes. Then first process grabs about 3 M/s of IO and suddenly dissapears (1-2 sec). Then second process does about 7.5 M/s of IO for around a 1-2 minutes. * Snapshot is successfuly created and is usable for reverting or extracting. * Pretty much the same behaviour occurs when command 'savevm' is issued directly from qemu monitor, without using libvirt at all (actually, virsh snapshot-create just calls 'savevm' to the monitor socket). * This behaviour was observed on lucid, meerkat, natty and even with git version of libvirt (f44bfb7fb978c9313ce050a1c4149bf04aa0a670). Also slowsave packages from https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/524447 gave this issue. Thank you for helping to solve this issue! ProblemType: Bug DistroRelease: Ubuntu 11.04 Package: libvirt-bin 0.8.8-1ubuntu5 ProcVersionSignature: Ubuntu 2.6.38-7.38-server 2.6.38 Uname: Linux 2.6.38-7-server x86_64 Architecture: amd64 Date: Thu Mar 24 12:19:41 2011 InstallationMedia: Ubuntu-Server 10.04.2 LTS "Lucid Lynx" - Release amd64 (20110211.1) ProcEnviron: LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: libvirt UpgradeStatus: No upgrade log present (probably fresh install)
