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[libvirt-users] Migrating a LV backed guest
by Corey Quinn 18 Oct '12

18 Oct '12

I have a KVM VM that's backed by a logical volume on local disk. I'd like to copy / move it to an identically configured host. [root@virt2 cquinn]# virsh migrate --copy-storage-all --verbose --persistent node1.www qemu+ssh://10.102.1.11/system error: Unable to read from monitor: Connection reset by peer How should I effectively troubleshoot this? Am I misunderstanding how virsh migrate is supposed to work? Regards, Corey Quinn

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[libvirt-users] cgroup blkio.weight working, but not for KVM guests
by Ben Clay 17 Oct '12

17 Oct '12

I'm running libvirt 0.10.2 and qemu-kvm-1.2.0, both compiled from source, on CentOS 6. I've got a working blkio cgroup hierarchy which I'm attaching guests to using the following XML guest configs: VM1 (foreground): <cputune> <shares>2048</shares> </cputune> <blkiotune> <weight>1000</weight> </blkiotune> VM2 (background): <cputune> <shares>2</shares> </cputune> <blkiotune> <weight>100</weight> </blkiotune> I've tested write throughput on the host using cgexec and dd, demonstrating that libvirt has correctly set up the cgroups: cgexec -g blkio:libvirt/qemu/foreground time dd if=/dev/zero of=trash1.img oflag=direct bs=1M count=4096 & cgexec -g blkio:libvirt/qemu/background time dd if=/dev/zero of=trash2.img oflag=direct bs=1M count=4096 & Snap from iotop, showing an 8:1 ratio (should be 10:1, but 8:1 is acceptable): Total DISK READ: 0.00 B/s | Total DISK WRITE: 91.52 M/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND 9602 be/4 root 0.00 B/s 10.71 M/s 0.00 % 98.54 % dd if=/dev/zero of=trash2.img oflag=direct bs=1M count=4096 9601 be/4 root 0.00 B/s 80.81 M/s 0.00 % 97.76 % dd if=/dev/zero of=trash1.img oflag=direct bs=1M count=4096 Further, checking the task list inside each cgroup shows the guest's main PID, plus those of the virtio kernel threads. It's hard to tell if all the virtio kernel threads are listed, but all the ones I've hunted down appear to be there. However, when running the same dd commands inside the guests, I get roughly-equal performance - nowhere near the ~8:1 relative bandwidth enforcement I get from the host: (background ctrl-c'd right after foreground finishes, both started within 1s of each other) [ben@foreground ~]$ dd if=/dev/zero of=trash1.img oflag=direct bs=1M count=4096 4096+0 records in 4096+0 records out 4294967296 bytes (4.3 GB) copied, 104.645 s, 41.0 MB/s [ben@background ~]$ dd if=/dev/zero of=trash2.img oflag=direct bs=1M count=4096 ^C4052+0 records in 4052+0 records out 4248829952 bytes (4.2 GB) copied, 106.318 s, 40.0 MB/s I thought based on this statement: "Currently, the Block I/O subsystem does not work for buffered write operations. It is primarily targeted at direct I/O, although it works for buffered read operations." from this page: https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/ht ml/Resource_Management_Guide/ch-Subsystems_and_Tunable_Parameters.html that this problem might be due to host-side buffering, but I have that explicitly disabled in my guest configs: <devices> <emulator>/usr/bin/qemu-kvm</emulator> <disk type="file" device="disk"> <driver name="qemu" type="raw" cache="none"/> <source file="/path/to/disk.img"/> <target dev="vda" bus="virtio"/> <alias name="virtio-disk0"/> <address type="pci" domain="0x0000" bus="0x00" slot="0x04" function="0x0"/> </disk> Here is the qemu line from ps, showing that it's clearly being passed through from the guest XML config: root 5110 20.8 4.3 4491352 349312 ? Sl 11:58 0:38 /usr/bin/qemu-kvm -name background -S -M pc-1.2 -enable-kvm -m 2048 -smp 2,sockets=2,cores=1,threads=1 -uuid ea632741-c7be-36ab-bd69-da3cbe505b38 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/background.monitor,server,n owait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/path/to/disk.img,if=none,id=drive-virtio-disk0,format=raw,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virti o-disk0,bootindex=1 -netdev tap,fd=20,id=hostnet0,vhost=on,vhostfd=22 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=00:11:22:33:44:55,bus=pci.0,addr= 0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -device usb-tablet,id=input0 -vnc 127.0.0.1:1 -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 For fun I tried a few different cache options to try to force a bypass the host buffercache, including writethough and directsync, but the number of virtio kernel threads appeared to explode (especially for directsync) and the throughput dropped quite low: ~50% of "none" for writethrough and ~5% for directsync. With cache=none, when I generate write loads inside the VMs, I do see growth in the host's buffer cache. Further, if I use non-direct I/O inside the VMs, and inflate the balloon (forcing the guest's buffer cache to flush), I don't see a corresponding drop in background throughput. Is it possible that the cache="none" directive is not being respected? Since cgroups is working for host-side processes I think my blkio subsystem is correctly set up (using cfq, group_isolation=1 etc). Maybe I miscompiled qemu, without some needed direct I/O support? Has anyone seen this before? Ben Clay rbclay(a)ncsu.edu

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[libvirt-users] Migrating fails with "Timed out during operation: cannot acquire state change lock"
by Guido Winkelmann 17 Oct '12

17 Oct '12

Hi, After recently upgrading to 0.9.11 (as shipped with Fedora 17), I was just trying to migrate a qemu domain from one host to another (using virDomainMigrateToURI()), when I got this error message: Unsafe migration: Migration may lead to data corruption if disks use cache != none Okay, this is explainable (if a bit disappointing - I would have hoped that qemu would be able to disable disk caches before migration and then reenable them afterwards...). However, the next time I tried migrating the same domain, I got this error message after about 30 seconds: Timed out during operation: cannot acquire state change lock This looks like a bug to me - granted not a high profile one if it only happens when someone is retrying a failed migration, but still... Guido

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[libvirt-users] Connection using Java
by Felipe Oliveira Gutierrez 16 Oct '12

16 Oct '12

Hi, I am using java to connect to the xen, but my class is throwing a exception. Does anyone know what is happening? public class TestConnection { public static void main(String[] args) { Connect conn = null; try { conn = new Connect("xen+ssh://root@192.XXX.XXX.XX/", true); libvir: RPC error : End of file while reading data: nc: invalid option -- 'U' nc -h for help: Input/output error exception caught:org.libvirt.LibvirtException: End of file while reading data: nc: invalid option -- 'U' nc -h for help: Input/output error level:VIR_ERR_ERROR code:VIR_ERR_SYSTEM_ERROR domain:VIR_FROM_RPC hasConn:false hasDom:false hasNet:false message:End of file while reading data: nc: invalid option -- 'U' nc -h for help: Input/output error str1:%s str2:End of file while reading data: nc: invalid option -- 'U' nc -h for help: Input/output error str3:null int1:-1 int2:-1 Thanks, Felipe -- *-- Felipe Oliveira Gutierrez* *-- **lipe.82(a)gmail.com* <lipe.82(a)gmail.com> *-- https://sites.google.com/site/lipe82/Home/diaadia*

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[libvirt-users] LXC guest memory recycling under RHEL6
by Rudy Godoy Guillén 14 Oct '12

14 Oct '12

Hello, I'm running a LXC guest using libvirtd under RHEL6. The guest has this particular memory behavior that I'm unable to explain. I've the following memory settings for this guest's memory. Inside the guest I'm running a Apache webserver serving PHP scripts and static content. <memory unit='GB'>2</memory> <currentMemory unit='GB'>2</currentMemory> <memtune> <hard_limit unit='GB'>2</hard_limit> </memtune> Now, when querying using virsh dominfo I see the amount of used RAM increases every second and it gets to the point where it reaches the limit causing the guest to be unresponsive. The current solution is destroying the guest process (virsh destroy) and starting again, but the behavior repeats again. As I understand what is happening is that the amount of memory used by Apache's processes (4 mpm forks) is never released so every request causes more memory comsumption reaching that point. If I'm correct on this what can I do to handle it? thanks! -- Rudy Godoy http://stone-head.org

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[libvirt-users] What to configure for a guest with 2.2. kernel ...
by Stefan G. Weichinger 12 Oct '12

12 Oct '12

Greetings, libvirt-users ... I ask for help with virtualizing an ancient machine with a linux kernel 2.2. I already succeeded doing that but I face random performance issues and I somehow get lost in all the settings and options. I am using Virtual Machine Manager: * I can't chose something like Linux for the OS and 2.2 for the kernel. Does the combination "linux/2.4 kernel" work or should I choose "Other" or "Generic" ? * Later there I get a choice of "Architektur" (or "architecture" ? german here): for a 32bit-guest, should it be "i686" to reflect the environment for the guest or "x86_64" to fully use the potential of the host? Please forgive my questions, maybe they are FAQ somewhere, I really fiddled a lot already ... Thanks, Stefan

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[libvirt-users] Libvirt mpiexec networking issue
by Shawn Furrow 12 Oct '12

12 Oct '12

Hi all, Not sure if this is the best place to put this question since I'm not sure if it's a Libvirt issue but... I currently have two VMs up with networking and I can successfully ssh to and from each VM and I have confirmed that I can successfully download things from the internet. However, when trying to run mpiexec (which uses ssh), the connection fails and gives me the following errors: [proxy:0:0@guestVM] HYDU_sock_connect (./utils/sock/sock.c:188): unable to connect from "guestVM" to "guestVM" (Connection refused) [proxy:0:0@guestVM] main (./pm/pmiserv/pmip.c:205): unable to connect to server guestVM at port 56514 (check for firewalls!) Just so it is clear, I know that the two guests host names are the same (they are clones) but I am giving explicit IP address for the connection so it should not be an issue. Does any one know if there is something unique with how Libvirt networking is set up that would cause such an error? I have tried checking for firewalls and there don't seem to be any. Thanks, Shawn -- Virginia Tech Bradley Department of Electrical and Computer Engineering B.S. Electrical Engineering B.S. Computer Engineering

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[libvirt-users] libvirt java api create volume bug?
by zhijun liu 12 Oct '12

12 Oct '12

hi,all I use libirt Java AP { pool.storageVolCreateXML(xml,0)} to create a volume ,notice:here I define the format is "qcow2", the xml file is : <volume> <name>volume8</name> <capacity unit="KB">512000</capacity> <target> <format type="qcow2" /> </target> </volume> when use command check the volume's format, root@60:/dev/vgtest2# qemu-img info volume8 image: volume8 file format: raw virtual size: 500M (524288000 bytes) disk size: 0 I think this is a bug.can you fix it? the libvirt version is 0.9.8 libivrt-java version is 0.4.9 os:ubuntu12.04 thanks liuzhijun

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[libvirt-users] Libvirt Error guest wont start
by Shawn Furrow 11 Oct '12

11 Oct '12

Hi all, I have been using Libvirt for several months now and I have only had minimal problems. I had a particular setup and was starting up multiple guests just fine. However, with seemingly no changes I now get the following error when trying to start a guest: virsh start guest0 error: Failed to start domain guest0 error: internal error Process exited while reading console log output: Supported machines are: pc Standard PC (alias of pc-0.12) pc-0.12 Standard PC (default) pc-0.11 Standard PC, qemu 0.11 pc-0.10 Standard PC, qemu 0.10 isapc ISA-only PC Apparently, the machine argument settings were changed in recent versions of Libvirt. Or at least that is what it seems. My guest's OS settings were: <os> <type arch='x86_64' machine='pc-1.1'>hvm</type> <boot dev='hd'/> </os> After getting this error I tried setting the machine argument to one of the "supported" ones. Then I get this error: virsh start guest0 error: Failed to start domain guest0 error: Unable to read from monitor: Connection reset by peer Anyone have any ideas as to why this happened all of a sudden? I was not having any problems before. Thanks, Shawn -- Virginia Tech Bradley Department of Electrical and Computer Engineering B.S. Electrical Engineering B.S. Computer Engineering

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[libvirt-users] virsh start failed (Failed to query file context on ...)
by Binknight 11 Oct '12

11 Oct '12

hi all, I try to follow the instructions in http://libvirt.org/drvlxc.html to config libvirt-lxc, but failed when starting the lxc. The domain config file: # cat b.xml <domain type='lxc'> <name>b</name> <memory>32768</memory> <os> <type>exe</type> <init>/bin/sh</init> </os> <vcpu>1</vcpu> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>destroy</on_crash> <devices> <emulator>/usr/libexec/libvirt_lxc</emulator> <filesystem type='mount'> <source dir='/data/lxc/centos6'/> <target dir='/'/> </filesystem> <interface type='network'> <source network='default'/> </interface> <console type='pty' /> </devices> </domain> then define it: # virsh --connect lxc:/// define b.xml Domain b defined from b.xml then start: # virsh --connect lxc:/// start b error: Failed to start domain b error: internal error guest failed to start: 2012-10-10 09:56:17.369+0000: 452722: info : libvirt version: 0.9.10, package: 21.el6_3.4 (CentOS BuildSystem <http://bugs.centos.org>, 2012-08-23-18:28:26, c6b9.bsys.dev.centos.org) 2012-10-10 09:56:17.369+0000: 452722: error : lxcControllerRun:1484 : Failed to query file context on /data/lxc/centos6: No data available It's the filesystem mount section that cause this problem. The tutorial says the path '/data/lxc/centos6' should be "private root filesystem (perhaps hand-crafted using busybox, or installed from media, debootstrap, whatever)", but I am not quite clear about what this path should be. In my case, the "/data/lxc/centos6" is the root of template downloaded from http://wiki.openvz.org/Download/template/precreated. # pwd /data/lxc/centos6 # ls bin boot dev etc fastboot home lib media mnt opt proc root sbin selinux srv sys tmp usr var Can someone elaborate what should <source dir='/data/lxc/centos6'/> be? many thanks

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