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1612 discussions

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

4 3

top on host and guest
by Markus Falb 21 Jul '12

21 Jul '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, I have a 6.3 guest running on a 6.3 host and the output from top seems strange to me. At least I did not expect this. While in the guest on core is busy with i/o the host seems idle. Does anyone know why it is this way? See the output from top below, first the one from guest, then host. top - 14:12:35 up 12 min, 1 user, load average: 2.76, 2.28, 1.24 Tasks: 169 total, 1 running, 168 sleeping, 0 stopped, 0 zombie Cpu0 : 0.3%us, 0.7%sy, 0.0%ni, 0.0%id, 99.0%wa, 0.0%hi, 0.0%si, Cpu1 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu2 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu3 : 0.0%us, 0.3%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, top - 14:14:28 up 15 min, 1 user, load average: 0.79, 0.84, 0.50 Tasks: 238 total, 2 running, 236 sleeping, 0 stopped, 0 zombie Cpu0 : 5.7%us, 1.0%sy, 0.0%ni, 93.3%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu1 : 0.3%us, 0.3%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu2 : 0.7%us, 1.0%sy, 0.0%ni, 98.3%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu3 : 0.3%us, 0.3%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu4 : 3.0%us, 0.7%sy, 0.0%ni, 96.4%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu5 : 0.0%us, 0.7%sy, 0.0%ni, 98.3%id, 0.0%wa, 0.0%hi, 1.0%si, Cpu6 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, Cpu7 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, - -- Kind Regards, Markus Falb -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlAKo0EACgkQYoWFBIJE9eViHwCgv62wNVrVOMFVikZmlsWdq0p3 TuYAn2hlEjJRd+1VE50qGr9X9Pd/JFwo =fRax -----END PGP SIGNATURE-----

2 1

PXE boot of KVM virtual fails
by centos 10 Jul '12

10 Jul '12

Hi, excuse me if I make any faux-pas this is the first time I've posted to a list. Can someone confirm that it is possible to PXE boot a KVM virtual machine from another KVM virtual machine? I have a virtual x86_64 Centos 6.2 server running DHCP and TFTP. The plan is to kickstart a new KVM machine - purely so I can get my head around PXE and kickstart (I've not used either before). From the output I'm seeing it would appear that the DHCP is working ok, and that the boot loader (pxelinux.0) is being sent via TFTP, but then I'm seeing a couple of errors. Firstly I get... tftp://172.168.1.101/pxelinux.0.. Not supported (0x3c126003) then I get.... Could not load tftp://172.168.1.101/pxelinux.0: Not supported (0x3c126003) No more network devices. I have a feeling that this is indicating that the PXE boot loader (pxelinux.0) isn't compatible with the virtual network card - I've tried most of the NICs available, and I've tried gpxelinux.0 and some of the files provided by gpxe-roms-qemu (though I have to admit I'm not sure if I need to do something with those files to make them boot loaders?). My biggest worry is that I'm trying to do something nonsensical, but if not - has anyone managed to get this to work? Cheers, Martin

1 0

Virtual NICs on a Xen VM
by Steve Campbell 08 Jul '12

08 Jul '12

Currently, I've got a Centos 5.8 host that I began playing with Xen virtual machines. It's a sandbox sort of server where I try and learn all of this virtualization stuff. In the future, I'll more than likely swith to Centos 6 and kvm, but for now, it's xen. Searching google and the list, I can't find an explanation of how to add a second virtual NIC to a running VM when I only have one real NIC on the server. For the most part, in my searches it appears that I need a real second NIC on the server to do this. I can find a few examples, but each sort of implies it a one-to-one minimum of real hardware to virtual hardware. So what I'm asking is "Is it possible to create a xen VM that has two virtual ethernet interfaces on a host that has only one real NIC"? I'd like to simulate a server that I can make a firewall out of and to do that would mean I need an internal and external interface. I'm attempting to create a set of firewalls in a highly available environment to test with. So far, most of the docs I find are for more complex people than I. There's concepts like virtual switches and the like that are creeping into the reading, so the more I read, the more overwhelmed I am. Did I mention I'm still just starting to explore virtualization? If someone can provide me with a possible yes-no answer and maybe a link to documentation that might explain the way, I'll gladly do all my own grunt work. Thanks for any and all help. steve campbell

4 3

Has anyone been able to start a Fedora 16 VM in Xen PV?
by Scot P. Floess 08 Jul '12

08 Jul '12

All, I've had a heck of a time getting Fedora 16 to run as a guest VM under CentOS 5.7 host as a paravirtualized Xen guest. I believe the issue has something to do with Fedora 16 using grub2... When I attempt to start the VM (via xm create), I get this error: Using config file "/etc/xen/fedora-workstation". Traceback (most recent call last): File "/usr/bin/pygrub", line 686, in ? fs = fsimage.open(file, get_fs_offset(file)) IOError: [Errno 95] Operation not supported No handlers could be found for logger "xend" Error: Boot loader didn't return any data! In my kickstart, I had to create a partition for F16 as: part biosboot --fstype=biosboot --size=1 I didn't readily find the error when googling... Has anyone been able to run F16 as a PV guest? And if so, what did you do to make it happen????? Thanks!!!!!!!!!!!!! Scot P. Floess RHCT (Certificate Number 605010084735240) Chief Architect FlossWare http://sourceforge.net/projects/flossware http://flossware.sourceforge.net https://github.com/organizations/FlossWare

6 10

centos6 and xen4 dom0 memory allocation
by Peter Peltonen 08 Jul '12

08 Jul '12

Hi, This is slightly OT as xen is not officially supported in EL6. But maybe someone else is running it on centos6 as well and could help me out here: I have problems allocating a static amount of memory for my xen dom0. It seems to reduce when new domUs are created, even though I *think* ballooning is disabled. Can someone advise me what I'm doing wrong? I have xen-4.1.1-3 installed from http://xenbits.xen.org/people/mayoung/EL6.xen on my centos6 server. I am running 2.6.32-131.12.1.el6.xendom0.x86_64 kernel available from the same place. 'xl info' reports about available memory as follows: total_memory : 24567 free_memory : 3698 xen_commandline : dom0_mem=2048M and in xend-config.sxp I have: (dom0-min-mem 256) (enable-dom0-ballooning no) (total_available_memory 0) Now one would think that I should have 2048M memory for dom0, right? I started from there, but when starting domUs it has been reduced to 1140M even though I think ballooning is disabled and there is free memory available? And the weird thing is that dom0 has done some swapping: # free -mt total used free shared buffers cached Mem: 1140 1052 88 0 2 12 -/+ buffers/cache: 1038 102 Swap: 8194 85 8109 Total: 9335 1138 8197 Shutting down domUs and making more memory available does not reverse the effect, dom0 does not allocate more memory. What am I missing here or is my xen setup acting strangely here? Best regards, Peter

2 4

centos6.2 install Virtualization
by gang ao 30 Jun '12

30 Jun '12

Today when I run " yum groupinstall "Virtualization*" " on my server ,It retunes just like this : Warning: Group virtualization-tools does not have any packages. Package virt-who-0.3-3.el6.noarch already installed and latest version Package libvirt-client-0.9.4-23.el6_2.9.i686 already installed and latest version Package libvirt-0.9.4-23.el6_2.9.i686 already installed and latest version Warning: Group virtualization-platform does not have any packages. Package virt-manager-0.9.0-7.el6.i686 already installed and latest version Package python-virtinst-0.600.0-5.el6.noarch already installed and latest version Package virt-viewer-0.4.1-7.el6.i686 already installed and latest version Package virt-top-1.0.4-3.11.el6.i686 already installed and latest version Warning: Group virtualization-client does not have any packages. Warning: Group virtualization does not have any packages. What does the "does not have any packages" mean?Is it because of my CPU doesn't support Virtualization or because my yum resource doesn't have the Virtualization packages? ths for reading and looking forward to be replied.

2 2

Convert EXT3/EXT4 to XFS
by Karthick K 28 Jun '12

28 Jun '12

Hi Folks, Can you guide me about how to convert the CentOS file system from EXT3/EXT4 to XFS without loosing data? I have tried search in google about this but I couldn't get the relevant idea. **

2 1

Basic shared storage + KVM
by Andrea Chierici 27 Jun '12

27 Jun '12

Hi, I am trying to set up a shared iscsi storage to serve 6 kvm hypervisors running centos 6.2. I export an LVM from iscsi and configured virt-manager to see the iscsi space as LVM storage (a single storage pool). I can create space on this LVM storage pool directly from virt-manager and I am already running a couple of sample VMs, that do migrate from one hv to the other. This configuration has a problem: when I create a new LV on the LVM storage pool to host a new VM, the HV where I am creating the virtual machine on sees the LV as status "available", while the others see it as "NOT available". In some circumstances this can crash libvirtd. To fix this I generally issue: vgchange -an; sleep 1; vgchange -ay but sometimes this fails with error: device-mapper; create ioctl failed: Device or resource busy and anyway it's not very convenient to issue this command on every node every time a new LV is created. Can anyone suggest a solution (if any) to this problem? Keep in mind that the basic concept behind this approach is to keep things as simple as possible. I don't want to configure a cluster or any other complicated tool to simply be able to migrate VMs from one HV to another. Thanks, Andrea -- Andrea Chierici - INFN-CNAF Viale Berti Pichat 6/2, 40127 BOLOGNA Office Tel: +39 051 6092809 ICQ#2328798, MSN#ataruz<at>gmail.com, Skype#ataruz --

4 5

Fencing question(s)
by Steve Campbell 21 Jun '12

21 Jun '12

I've got a Centos 5.8 box that I use for testing Xen VMs. I'm trying to setup some Centos 6.2 hosts in a high availability situation. I've tried the pacemaker route and couldn't get the connection established, so thought I'd try the RH-preferred methods. Mind you, all of these VMs are on the same host. Using Conga, it seems that I need some sort of fencing device, which doesn't really work in a VM environment. I'm guessing it's the same with command line configuration. Firstly, is it really possible to set up two VMs on the same machine to do HA? I can't see why not, but I'm not the best source of knowledge on any of this. Secondly, is there a useable fencing device that would work in a virtual environment for me to test with? I'd really like to avoid fencing altogether, even once in production, but every thing I read suggests against that. Any type of reply would be appreciated. steve campbell

2 1

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