November 2010 - virt - lists.centos.org

IBM GPFS filesystem
by Adam Wead 03 Dec '10

03 Dec '10

Hi all, I was wondering if anyone might be able to speak about using IBM's GPFS filesystem as a means of storing virtual guests in a clustered environment with CentOS as the nodes and KVM as the hypervisor? I'm looking at using IBM's TSM software for archiving data from disk to tape. This requires buying a license for GPFS which is used in conjunction with TSM but can also be used as a clustered filesystem as well. As I understand it, GPFS can work with CentOS so long as you're using the right kernel. Is anyone out there using CentOS+GPFS for their virtualization environment? many thanks in advance, ...adam

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PXDI; Automated Xen 4.0.1 + 2.6.32 dom0 installer for RHEL 6
by Digimer 23 Nov '10

23 Nov '10

I tool Pasi Kärkkäinen's tutorial[1] that he announced on Thursday and turned it into an automated installation program called PXDI. - http://wiki.alteeve.com/index.php/Pxdi I've tested it on ~9 machines and, so far, it has worked. Of course, this is a small sample set and could use much more testing. *hint* :) As it is built now, it can take a "minimal" Red Hat Enterprise Linux 6.0 x86_64 install (+perl) and completely built and install qemu, (patched) libvirt, xen 4.0.1 and a 2.6.32 dom0. It also adds itself to /boot/grub/grub.conf, so it should be a matter of run, wait, reboot, done. *PLEASE* don't run it on a server you care about. I have done my best to avoid errors, but I can make promises that it won't mess up your machine. Run it on test servers only, please, until more testing is done. If the installer aborts at any time, it is smart enough to (mostly) know what has already been done and will pick up where it left off. So it should be safe to run several times if needed without problem. Of course, I hope one run will be enough. :) Eventually we hope to have RPMs in repos so most users won't need this. For now though, I hope this will do. I would *love* to hear feedback; Good, bad or otherwise! Digimer 1. http://wiki.xen.org/xenwiki/RHEL6Xen4Tutorial -- Digimer E-Mail: digimer(a)alteeve.com AN!Whitepapers: http://alteeve.com Node Assassin: http://nodeassassin.org

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How does KVM handle multiple cores?
by MargoAndTodd 22 Nov '10

22 Nov '10

Hi All, How does KVM handle multiple cores. I have an x5650 with 6 real cores that presents itself to my OS as 12 virtual cores (hyperthreading). Does KVM see 6 or 12 cores. And, can I tell KVM how many cores I want it to use? Am I misunderstanding how KVM works? What I am after is if my guest is 100% busy, I still want some power left over for my host. Many thanks, -T

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KVM and Windows "/use pmtimer"
by Eric Searcy 21 Nov '10

21 Nov '10

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Virtualiz… Want to get some more people's opinion on this: the above doc says to use the boot parameter "/use pmtimer" to use the RTC "instead of the TSC for all time sources which resolves guest timing issues". One: does this have any bearing on whether the host has the constant_tsc flag (i.e. are all the sections that follow "Configuring hosts without a constant Time Stamp Counter" subordinate to it, or does that just have bearing on power management on that one CPU listed---AMD rev F)? Other question: http://support.microsoft.com/kb/938448 implies that for 2003 SP2 "/use pmtimer" shouldn't be needed as it will use the platform timer (RTC) if you have ACPI or APIC present. ("By default, Windows Server 2003 Service Pack 2 (SP2) uses the PM timer for all multiprocessor Advanced Programmable Interrupt Controller (APIC) Hardware Abstraction Layers (HALs) or Advanced Configuration and Power Interface (ACPI) HALs".) Anybody have any experience as to whether this (using ACPI feature in KVM) resolves the timing issues without needing pmtimer explicitly set? Thanks, Eric

2 1

What are KVM guest cores?
by MargoAndTodd 20 Nov '10

20 Nov '10

Hi All, What are guest cores in KVM? Are they fake, like everything else in the guest? Just another process running on the host emulating a core? Or are the guest cores actually connected directly to the physical cores on my motherboard? Many thanks, -T

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what scheduling algorithm does KVM use?
by Nick 19 Nov '10

19 Nov '10

This may not be the best place to ask, but I was prompted by a question about guest cores on KVM. We currently use VMWare Server (v1.0) on CentOS5. It supports up to two virtual CPUs, but not very well, as I understand it. VMWare Server 2.0 might do better at supporting the same maximum of 2 CPUs, but if my research is correct, they both use what is called "strict co-scheduling". Which means, if a two virtual-CPU VM is waiting for a time slice on the physical host, there needs to be two physical CPUs available to be allocated. This is because amount of time scheduled to each virtual CPU has to stay equal, else assumptions in the virtualised software may become false and things start going wrong. The problem with this is that it is obviously more of a constraint to have two physical CPUs available. Therefore adding virtual CPUs to a co-scheduled VM can actually make performance worse if the physical CPUs are under any sort of contention. Performance degrades rapidly under load - which is exactly what you don't want for a webserver. Therefore advice seems to be to avoid using multi-virtual CPU VMs. [1] VMWare ESX uses something supposedly better, called relaxed co-scheduling. [2]. We're not likely to use that any time soon, since we are using 1&1 root servers running CentOS. I did try and research the algorithm(s) used by KVM. Apparently it doesn't use co-scheduling, but possibly something called the "completely fair scheduler", but I'm no an expert in VM scheduling and I didn't manage to discover what this means, nor specifically what the implications are for performance were in terms of scaling up the number of virtual CPUs on KVM. (I understand that the number of virtual CPUs supported by KVM is be quite high.) Anyway, I've been asked how to scale a VM up utilise more - say four or more - physical CPUs. Is KVM better at this than VMware Server, or does the same basic problem persist? Thanks, Nick 1. http://communities.vmware.com/thread/169323 http://cs.gmu.edu/~hfoxwell/cs671projects/southern_v12n.pdf > "The SMP > scheduling algorithms used by ESX server and by Xen > have a low overhead for single-threaded compute inten- > sive workloads. However, they do not scale as well for > multi-threaded workloads on a system with overcommit- > ted CPU resources." 2. http://communities.vmware.com/thread/157849 http://communities.vmware.com/docs/DOC-4960 http://communities.vmware.com/docs/DOC-5501

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SPICE Benchmark
by Alexey Vasyukov 19 Nov '10

19 Nov '10

Hi folks. We finally finished our work on benchmarking SPICE and would like to share the results. Detailed report in English: http://www.bureausolomatina.ru/sites/default/files/SPICE%20Benchmark%20-%20… The report provides benchmark results of SPICE network load for different types of workload. SPICE operation on limited low-speed network connection was also tested. The results were compared with similar tests for RDP. Testing was based on SPICE version 0.4.3. This version is not the latest one but it is used currently in RHEV-D 2.2 and also in RHEL6. So, we guess, the results are pretty useful. We are going to test SPICE 0.6 in nearest future because it has very interesting WAN improvements. So, we welcome any comments, critics or advices. Best regards, Alexey Vasyukov

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[HOWTO] Running Xen 4.0 host (dom0) with Redhat Enterprise Linux 6 (RHEL6)
by Pasi Kärkkäinen 19 Nov '10

19 Nov '10

Hello, If you're interested in running Xen 4.0 hypervisor/dom0 on RHEL6, take a look at here: http://wiki.xen.org/xenwiki/RHEL6Xen4Tutorial It explains steps needed to rebuild Xen 4.0.1 src.rpm from Fedora on RHEL6, and how to fetch dom0 capable 2.6.32.x kernel from upstream git repository. It also shows how to get libvirt/virt-manager working with Xen on RHEL6. Hopefully it helps :) -- Pasi

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Gilberto Nunes wants to stay in touch on LinkedIn
by Gilberto Nunes 18 Nov '10

18 Nov '10

LinkedIn ------------ Discussion, I'd like to add you to my professional network on LinkedIn. - Gilberto Nunes Gilberto Nunes Owner at Konnecta Consulting Itajaí Area, Brazil Confirm that you know Gilberto Nunes https://www.linkedin.com/e/anzi98-ggmu3q30-6f/isd/1918541538/YqPt7-wa/ -- (c) 2010, LinkedIn Corporation

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Re: [CentOS-virt] KVM: where are the directions?
by jayeola＠gmail.com 15 Nov '10

15 Nov '10

rpm -ql kvm rpm -qa | grep kvm /sys/john == /dev/BlackBerry

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Can I mix kvm and virtual box?
by MargoAndTodd 15 Nov '10

15 Nov '10

Hi All, On my customer's CentOS 5.5 x64 server, I have Virtual Box installed. To make a side by side comparison, I would like to also run KVM. I read somewhere that this can not be done, but I can not remember where. Am I able to mix the two so I can demonstrate the differences to my customer? Many Thanks, -T

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Does KVM have a shared clipboard?
by MargoAndTodd 12 Nov '10

12 Nov '10

Hi All, Does KVM have a shared clipboard, such that I can copy and paste between guest and host? Many thanks, -T

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Can KVM be run "headless"?
by MargoAndTodd 11 Nov '10

11 Nov '10

Hi All, Can KVM be run "Headless", like Virtual Box? If so, how do I open a window to it? How do I start and stop it? Many thanks, -T

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KVM: where are the directions?
by MargoAndTodd 11 Nov '10

11 Nov '10

Hi All, I have been Googling my rear off. Where is the manual for KVM? It seems like the information is just all thrown about. Anyone know of a manual? A pdf? A home page with instructions? I am teachable (mostly). Many thanks, -T

1 2

Need sub for virtual box
by MargoAndTodd 11 Nov '10

11 Nov '10

Hi All, I am running Virtual box on a CentOS 5.5 x64 bit host. The guest is 23 bit Windows Server 2008 SP2 (not R2). Virtual Box bug 7606 is causing a customer of mine serious financial harm. http://www.virtualbox.org/ticket/7607#comment:3 I have tried in vain month or month over month to get Oracle to sell me a tech support contract, so that we can get some priority on this issue. No joy. I just get psycho babbled all over about "Reaching out to me". I have had it. Is there a good replacement for Virtual Box? requirements: 1) must run on CentOS 5.x as the host 2) must support Windows Server 2008 32 bit sp2 (not R2) as a guest 3) must support Supermicro X8SAX motherboard 4) must support the Intel x5650 processor (6 cores) 5) must actually work! Many thanks, -T

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Which is the best network interface to use.
by Rich 09 Nov '10

09 Nov '10

I am running centos 5.5 virtualized environment. I have 2 bridged network cards. My question is this. Should I be using virtual network or the shared physical device architecture?

2 1

vrit ip config
by ops Power Fag 08 Nov '10

08 Nov '10

cat /etc/sysconfig/network-scripts/ifcfg-eth0* # nVidia Corporation MCP61 Ethernet DEVICE=eth0 BOOTPROTO=static HWADDR=6C:F0:49:93:11:A3 IPADDR=192.168.182.237 NETMASK=255.255.255.0 ONBOOT=yes # nVidia Corporation MCP61 Ethernet DEVICE=eth0:1 BOOTPROTO=static IPADDR=192.168.182.238 NETMASK=255.255.255.0 ONBOOT=yes when reboot, ping show network down network up xend start network down how to fix this? datacenter charge me each time I need fix.

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dom0 network alias
by ops Power Fag 08 Nov '10

08 Nov '10

hi, I try to start xend on a server with network aliases and the network stack goes down. how to fix please? uses aliases on dom0 eth0 device amyone? <@tru_tru> opsPowerFag: try the centos-virt mailing list?

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Is kvm-clock dependant on hardware of Physical Server?
by Steven Ellis 04 Nov '10

04 Nov '10

I've got a three Centos 5.5 KVM severs, but only one of them is presenting guests with the kvm-clock source. The two servers I'm not seeing kvm-clock on have Athlon x2 64bit processors. The other server with kvm-clock has a Phenom II X6 1090T Processor. I've checked the system configuration and all the boxes have the same set of RPM packages. To confirm that the issue was physical hardware specific I migrated a VM from the Athlon to the Phenom server and the kvm-clock source appeared. Any ideas why I'm not seeing kvm-clock with my Athlon X2 processors, or is there another difference I haven't caught? Steve

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Conversion steps from Vmware server 2 to Centos KVM 5.5
by Tom Bishop 01 Nov '10

01 Nov '10

So I have finally carved out some time and need to start converting my vm's from Vmware server to KVM and I was wondering if anyone had the specfic steps that need to be taken...I understand how to convert the disks etc..what I am interested in is how to get them to use virtio ones which means iw ill need to remake initrd...so if anyone has moved from vmware server (aka the free one) to KVM and using the virtio drivers...if you have the complete steps that would be great...Thanks...**

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Xen on Centos 5.5 vs 5.3 and stability issues
by Steven Ellis 01 Nov '10

01 Nov '10

I've recently upgraded a Centos 5.3 machine to Centos 5.5. The hardware isn't HVM capabile so I'm only running para-virt guests. Using a vanilla i386 kernel boots without, but the newer kernel-xen locks up the Dom0 after a couple of minute. I'm only booting into single user mode for these tests so no VMs are active. *kernel-xen-2.6.18-128.1.10.el5 - no issues *kernel-xen-2.6.18-194.17.4.el5 - lock up *kernel-2.6.18-194.17.4.el5 - no issues For the moment I've switched back to the older Xen kernel, athough I'm still running the newer Xen Hypervisor. My current Xen packages are *xen-3.0.3-105.el5_5.5 *kernel-xen-2.6.18-194.17.4.el5 *kernel-xen-2.6.18-128.1.10.el5 *kmod-xfs-xen-0.4-2 *xen-libs-3.0.3-105.el5_5.5 *kernel-xen-devel-2.6.18-194.17.4.el5 *kernel-xen-devel-2.6.18-128.1.10.el5 *xen-devel-3.0.3-105.el5_5.5 Prior to the upgrade I had the following installed under Centos 5.3 *kernel-xen-devel-2.6.18-128.1.6.el5 *kernel-xen-2.6.18-128.1.10.el5 *xen-libs-3.0.3-80.el5_3.2 *xen-devel-3.0.3-80.el5_3.2 *kmod-xfs-xen-0.4-2 *kernel-xen-2.6.18-128.1.6.el5 *kernel-xen-devel-2.6.18-128.1.10.el5 *xen-3.0.3-80.el5_3.2 Booting Dom0 with kernel-xen-2.6.18-128.1.10.el5 everything appears to work normally and all of my Guests are up and running. If I boot with kernel-xen-2.6.18-194.17.4.el5 the boot normally gets to around udev and the system locks up. On a couple of occasions it did mange to boot but reported some files were corrupted. I'm worried that there is an issue running this kernel where the root file system is LVM on top of Raid 1. Anyone on this list have tips on diagnosing the issue, or come across a similar problem themselves. Steve

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virt November 2010