virt August 2012

virt@lists.centos.org

17 participants
7 discussions

SNMP monitoring
by Lars Hecking 03 Oct '12

03 Oct '12

It seems it's not possible to monitor kvm virtual image network interfaces via SNMP. MRTG's cfgmaker says ### The following interface is commented out because: ### * has no ifSpeed property and other monitors are consistently reporting that vm's interfaces are exceeding traffic thresholds (even on lo ...). Which is no surprise if the threshold is zero. I found a hint on some Debian forum that this behaviour is caused by the virtio driver. So I was wondering, is it recommended or are there advantages to configuring one of the emulated drivers instead (ne2k_pci,i82551,i82557b, i82559er,rtl8139,e1000,pcnet)? Or can I "fake it" somehow in the vm's snmpd config?

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CentOS 6.2 / kvm / Windows XP sp3 guest crashes repeatedly after a few minutes
by Philip Bondi 27 Aug '12

27 Aug '12

Hello to all: Recently upgraded from CentOS 6.0 to 6.2 to get USB passthrough support by performing "yum update". USB passthrough works great, but now my Windows XP sp3 guest crashes repeatedly after a few minutes. [root@shackleton-eth0 log]# rpm -qa|egrep '(kvm|kernel|libvirt-|qemu)'|sort abrt-addon-kerneloops-2.0.4-14.el6.centos.x86_64 dracut-kernel-004-256.el6_2.1.noarch gpxe-roms-qemu-0.9.7-6.9.el6.noarch kernel-2.6.32-220.7.1.el6.x86_64 kernel-2.6.32-71.el6.x86_64 kernel-devel-2.6.32-220.7.1.el6.x86_64 kernel-devel-2.6.32-71.el6.x86_64 kernel-firmware-2.6.32-220.7.1.el6.noarch kernel-headers-2.6.32-220.7.1.el6.x86_64 libreport-plugin-kerneloops-2.0.5-20.el6.x86_64 libvirt-0.9.4-23.el6_2.6.x86_64 libvirt-client-0.9.4-23.el6_2.6.x86_64 libvirt-python-0.9.4-23.el6_2.6.x86_64 qemu-img-0.12.1.2-2.209.el6_2.4.x86_64 qemu-kvm-0.12.1.2-2.209.el6_2.4.x86_64 This message in /var/log/messages precedes every crash: [root@shackleton-eth0 log]# grep kvm /var/log/messages Mar 19 09:09:25 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 Mar 19 09:15:48 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 Mar 19 09:25:51 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 Mar 19 11:21:27 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 Mar 19 12:07:16 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 Mar 19 12:16:14 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 Mar 19 13:46:27 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 Mar 19 14:06:49 shackleton-eth0 kernel: kvm: 2889: cpu0 unhandled wrmsr: 0x198 data 0 CentOS 6.0 was stable. Windows XP sp3 did not crash. Formerly, I was running virtio-win-0.1-15.iso, but now upgraded to virtio-win-0.1-22.iso and Windows XP sp3 remains unstable.

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Accessing NTFS on host from XP/Win7 VM
by Rajagopal Swaminathan 22 Aug '12

22 Aug '12

Greetings, I have installed Centos 6.3 recently on bare metal (as dual boot with win 7) and want to access the existing NTFS through XP Guest. SELinux is enforcing and VM network is NAT. Google confused me more that educating me -- maybe I could not cobble up the right phrase. Any help appreciated. TIA It is my only system at home. -- Regards, Rajagopal

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KVM - Virtio drivers for Centos 5.1
by aurfalien 14 Aug '12

14 Aug '12

Hi all, Really enjoying KVM as I was a long time user of Xen. Both are cool, just enjoying the new thing. Wondering if any one could share some nuggets on how to get a Centos 5.1 VM guest to use virtio? Trying to use virtio over the ide. Thanks in advance, - aurf

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tuned-adm fixed Windows VM disk write performance on CentOS 6
by Julian price 12 Aug '12

12 Aug '12

On a 32bit Windows 2008 Server guest VM on a CentOS 5 host, iometer reported a disk write speed of 37MB/s The same VM on a CentOS 6 host reported 0.3MB/s. i.e. The VM was unusable. Write performance in a CentOS 6 VM was also much worse, but it was usable. (See http://lists.centos.org/pipermail/centos-virt/2012-August/002961.html) With iometer still running in the guest, I installed tuned on the CentOS 6 host and enabled the virtual-host profile. iometer showed the average disk write speed increasing immediately. A fresh iometer test reported a disk write speed of 80MB/s. I'm not sure if the tuned-adm virtual-host profile was available in 6.0 - it may be necessary to update to get it. http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Power_Man… Installation is quick & easy: yum install tuned tuned-adm profile virtual-host I'm surprised not to see any other posts on this subject. Maybe there's something peculiar about my setup that caused the dreadful write performance & tuned-adm happened to fix it. This problem has been a real headache and I'm extremely grateful to Philip Durbin and jimi_c for bringing the solution to my attention. The host server was rebuilt from scratch after a RAID1 simultaneous double disk failure (happily my DR strategy worked. Have you tested yours recently?). It appears that CentOS 6 has some different defaults (more conservative power saving?). Maybe upgrades don't change the defaults, so this issue only affects new CentOS 6 installs? The iometer settings were: 1000 sectors, 16 outstanding IOs, access specification: 16k, 0%read 0%random The figures I've reported above are the 'Total MBs per second' See http://www.iometer.org/doc/downloads.html In the process of researching the problem, 2 other quick & easy optimisations came to light, each adding a few more MB/s: - Set noatime. See: http://www.activoinc.com/blog/2009/08/25/setting-noatime-and-nodiratime-for… - Disable Windows disk cacheing: See http://pve.proxmox.com/wiki/Windows_2003_guest_best_practices On Windows 2008: Computer Mgmt -> Disk Mgmt -> Select Drive (system) -> properties -> Policies tab -> uncheck 'Optimize for quick removal'

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CentOS 6 kvm disk write performance
by Julian price 11 Aug '12

11 Aug '12

I have 2 similar servers. Since upgrading one from CentOS 5.5 to 6, disk write performance in kvm guest VMs is much worse. There are many, many posts about optimising kvm, many mentioning disk performance in CentOS 5 vs 6. I've tried various changes to speed up write performance, but northing's made a significant difference so far: - Install virtio disk drivers in guest - update the host software - Update RAID firmware to latest version - Switch the host disk scheduler to deadline - Increase host RAM from 8GB to 24GB - Increase guest RAM from 2GB to 4GB - Try different kvm cache options - Switch host from ext4 back to ext3 - Set noatime on the virtual disk image file Note: There is no encryption or on-access virus scanner on any host or guest. Below are some the block write figures in MB/s from bonnie++ with various configurations: First, figures for the hosts show that the CentOS 6 server is faster: 54 CentOS 5 Host 50 CentOS 5 Host 69 CentOS 6 host 70 CentOS 6 host Figures for a CentOS 6 guest running on the CentOS 5 host show that the performance hit is less than 50%: 30 CentOS 6 guest on CentOS 5 host with no optimisations 27 CentOS 6 guest on CentOS 5 host with no optimisations 32 CentOS 6 guest on CentOS 5 host with no optimisations Here are the figures a CentOS 6 guest running on the CentOS 6 host with various optimisations. Even with these optimisations, performance doesn't come close to the un-optimised guest running on the CentoOS 5 host: 5 No optimisations (i.e. same configuration as on CentOS 5) 4 deadline scheduler 5 deadline scheduler 15 noatime,nodiratime 14 noatime,nodiratime 15 noatime 15 noatime + deadline scheduler 13 virtio 13 virtio 10 virtio + noatime 9 virtio + noatime The CentOS 6 server has a better RAID card, different disks and more RAM, which might account for the better CentOS 6 host performance. But why might the guest write performance be so much worse? Is this a known problem? If so, what's the cause? If not, is there a way to locate the problem rather than using trial and error? Thanks, Julian

5 7

RAID: by host or within KVM?
by Kanwar Ranbir Sandhu 11 Aug '12

11 Aug '12

Hi Virtualizers, I just setup a CentOS 6 box (at home) to run as a KVM host. It's replacing an absolutely ancient CentOS 5 server that's running Xen. I have one OS drive, and two drives in RAID 1 with LVM on top which is being used as the KVM storage pool. I created a KVM that will run OpenMediaVault (OMV). OMV requires an OS drive (which is really a LVM), and a separate drive(s) to put all the media on. This is where I'm a little unsure on how to proceed. I think I have two options: 1. Let the KVM host manage the drives (i.e. RAID with LVM on top) and just assign the single volume to OMV. OMV will see it as one HD. 2. Assign the individual drives to the OMV KVM, and let OMV manage the RAID creation, management, etc. I'm not sure which one will perform better. My hunch is if the RAID management is left at the host level, I'll see better overall performance. Performance isn't exactly my number one goal here, but I don't want to kill it completely either by going the wrong way. On the other hand, if I let OMV do the RAID management for the media storage disks, I'll gain future flexibility because it'll be much easier to move OMV to bare metal. Which way should I go? What would you guys do? Regards, Ranbir -- Kanwar Ranbir Sandhu

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virt August 2012