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[libvirt-users] Behavior of disk caching with qcow2 disks
by Andrew Martin 14 Aug '14

14 Aug '14

Hello, I am running several virtualization servers with QEMU 1.4.x and libvirt 1.0.2 on Ubuntu 12.04 and am working on optimizing the cache= and aio= options for the virtual machines. These VM images are mostly qcow2, and are served both from a local ext4 filesystem (with data=ordered,barrier) and from an NFS mountpoint (with sync). The local filesystem sits on top of an md software RAID of SATA HDDs. I have read some conflicting information about which cache option is used by default. This documentation states that cache=writethrough is the default: http://www-01.ibm.com/support/knowledgecenter/linuxonibm/liaat/liaatbpkvmgu… However this SuSE documentation claims that QEMU 1.2.x and newer allows the driver to select which cache mode, and it often defaults to cache=writeback: https://www.suse.com/documentation/sles11/book_kvm/data/sect1_1_chapter_boo… Which is correct? How is the cache mode set by default (if cache= is not specified)? My second question is can cache=none be used safely on a local ext4 filesystem with no BBU? Since ext4 uses barriers, would writing to these qcow2 image files be safe? The kernel documentation about barriers states that "Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty". Does this apply to qcow2 VM images? Thanks, Andrew Martin

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[libvirt-users] Error when compiling libvirt 1.2.7 on CentOS 6.4
by Hongbin Lu 14 Aug '14

14 Aug '14

Hi, I was trying to follow this guide (http://libvirt.org/compiling.html) to compile libvirt1.2.7 on CentOS6.4. There is an error on executing "make". Below is the steps to reproduce and the error messages. Any help is appreciated. Thanks. $ sudo yum install gcc make gnutls-devel device-mapper-devel \ python-devel libnl-devel yajl-devel \ libxml2-devel libpciaccess-devel $ wget ftp://libvirt.org/libvirt/libvirt-1.2.7.tar.gz $ gunzip -c libvirt-1.2.7.tar.gz | tar xvf - $ cd libvirt-1.2.7/ $ ./configure --prefix=/usr --localstatedir=/var --sysconfdir=/etc --with-openvz=yes $ make ..... Making all in src make[2]: Entering directory `/home/ec2-user/libvirt-1.2.7/src' GEN libvirt_access.xml /bin/sh: -w: command not found make[2]: *** [libvirt_access.xml] Error 127 make[2]: Leaving directory `/home/ec2-user/libvirt-1.2.7/src' make[1]: *** [all-recursive] Error 1 make[1]: Leaving directory `/home/ec2-user/libvirt-1.2.7' make: *** [all] Error 2 $ make V=1 .......... /usr/bin/ld:libvirt.syms:3220: syntax error in VERSION script collect2: ld returned 1 exit status make[3]: *** [libvirt.la] Error 1 make[3]: Leaving directory `/home/ec2-user/libvirt-1.2.7/src' make[2]: *** [all] Error 2 make[2]: Leaving directory `/home/ec2-user/libvirt-1.2.7/src' make[1]: *** [all-recursive] Error 1 make[1]: Leaving directory `/home/ec2-user/libvirt-1.2.7' make: *** [all] Error 2

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[libvirt-users] provide http server path as vfat floppy/disk
by Vasiliy Tolstov 14 Aug '14

14 Aug '14

Hello. Is that possible to use some url (http/https) that contains files as source for floppy or block device? I can find only http://www.redhat.com/archives/libvir-list/2009-November/msg00604.html that says about local files and floppy, i can write/use fuse based fs , but may be libvirt/qemu have this internally? -- Vasiliy Tolstov, e-mail: v.tolstov(a)selfip.ru jabber: vase(a)selfip.ru

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[libvirt-users] Support live migration of OpenVZ container
by Hongbin Lu 14 Aug '14

14 Aug '14

Hi libvirt team, I was trying to migrate an OpenVZ domain from one host to another host. It seems that the live migration of OpenVZ container is there ( https://openvz.org/Migration_from_one_HN_to_another) but it haven't been integrated to libvirt yet. In particular, I ran the following commands and it failed: $ sudo virsh migrate --live --verbose --undefinesource 101 openvz+ssh:// root(a)10.12.1.39/system error: this function is not supported by the connection driver: virDomainMigrate3 Could anyone confirm if libvirt supports live migration of OpenVZ domain. If yes, please let me know the correct way to do that. If no, I would like to know if there is a plan to add support for that. I don't mind to submit a patch if your team likes to review it. Please let me know. Thanks. Best regards, Hongbin

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[libvirt-users] how virt-manager gets CPU usage of Guest
by Restituto Marcus Arevalo 13 Aug '14

13 Aug '14

Hi, Does anybody know how virt-manager is getting the CPU usage of the guests? I need to know how to get the CPU usage of the guests and this is the only way I can think of. In other words, how does virt-manager produce the graph of the CPU usage of EACH guest in KVM? I don't actually need the graph, I just need to get the percentage(%) since I'm trying to create a Java program to get the CPU usage of each guest in KVM. Thanks! regards, Marco

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[libvirt-users] Does libvirt have API to detect image format
by Jianfeng Tang 13 Aug '14

13 Aug '14

> I am using backing store when I create my volume. However, the backing store file is from another team, which can be either in raw or in qcow2 format. Is there a libvirt API to detect image format by given an image file? Or I have to run qemu-img? >

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[libvirt-users] [qemu-kvm] Network bandwidth limits via libvirt
by Romain Hardouin 13 Aug '14

13 Aug '14

Hi all, I try to understand why the interface bandwidth limits are not applied to my Ubuntu 12.04 VM (qemu-kvm driver) and I would need some insights. I spawn my VM with OpenStack and when I issue a dumpxml on my domain, I can see that bandwidth limits are set: <interface type='ethernet'> <mac address='02:68:b5:c6:fa:a5'/> <bandwidth> <inbound average='500' peak='500' burst='1000'/> <outbound average='500' peak='500'/> </bandwidth> <script path=''/> <target dev='tap68b5c6fa-a5'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> However when I send a big file with scp I don't see any limits applied to the transfer rate. I've checked the domain log and I didn't see any qemu command line argument related to bandwidth limits. Should I expect to see a specific argument like "bps_wr" for IO limits? Also, should I expect to see something in particular under the cgroup directory for the qemu instance? Or do network limits are managed in another way than with cgroups? Below some information about my hypervisor: % virsh -V Virsh command line tool of libvirt 1.2.2 See web site at http://libvirt.org/ Compiled with support for: Hypervisors: QEMU/KVM LXC UML Xen LibXL OpenVZ VMWare VirtualBox Test Networking: Remote Network Bridging Interface netcf Nwfilter VirtualPort Storage: Dir Disk Filesystem SCSI Multipath iSCSI LVM RBD Sheepdog Miscellaneous: Daemon Nodedev AppArmor Secrets Debug Readline Modular qemu-kvm: 2.0.0 Kernel: 3.2.0-64-generic Any hints will be appreciated :) Thanks, Romain

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[libvirt-users] IP/MAC antispoof-protection
by Anton Gorlov 11 Aug '14

11 Aug '14

Hi all. What right way to protect ip/mac spoofing for guests withnount dhcp and other 1 ip per guest?

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[libvirt-users] Passing literal -cpu model string to qemu
by Richard W.M. Jones 11 Aug '14

11 Aug '14

On aarch64 with -M virt, the default CPU model is cortex-a15 (a 32 bit CPU). This is IMHO a stupid default, but there we are. Therefore most users will need to pass the `-cpu cortex-a53' or `-cpu cortex-a57' flag to qemu, depending on a complex formula of their host CPU and if they are using TCG or not. However I cannot work out how to pass this through libvirt. The obvious one would be: <cpu><model>cortex-a57</model></cpu> This passes `-cpu host' which is both wrong and likely to be a bug. I tried adding various flags and studying the source, but it's extremely non-obvious how to do this. Also adding the following into cpu_map.xml didn't make any difference: --- a/src/cpu/cpu_map.xml +++ b/src/cpu/cpu_map.xml @@ -626,6 +626,11 @@ <vendor name='IBM'/> <pvr value='0x004b0100'/> </model> + </arch> +  + <arch name='aarch64'> + <model name='cortex-a53'/> + <model name='cortex-a57'/> </arch> </cpus> Ideas here? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/

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[libvirt-users] Windows 8 virtualized on a Linux host
by arnaud gaboury 10 Aug '14

10 Aug '14

I plan to dual boot w8 and Archlinux, and virtualize the same w8 machine with libvirt qemu/kvm. I already did the dual boot. I am now starting the virtualization. My plan was to use the w8 partition as a Disk volume pool [1]. Unfortunately, I didn't noticed only FAT32 was a valid format when I installed w8 on NTFS. I need to change my whole setup, but beforethat, I want to be sure libvirt does not accept NTFS. So please, can you confirm? Then, it seems I am in trouble as my readings let me think w8 will not install on FAT32. Am I correct? Now it sounds to me I am in a dead end. Does anyone have any hint to achieve my plan? Thank you for any suggestions. [1]http://libvirt.org/storage.html

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