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1613 discussions

Clock Sources under Centos 5.5
by Steven Ellis 27 Sep '10

27 Sep '10

I'm wondering under what circumstances the kvm-clock source is exposed to a guest. I've got a bunch of KVM servers running Centos 5.5 and some of the guests have are defaulting to jiffies or apic whilst some are picking up kvm-clock. Looking at the virtual machine definition file there doesn't appear to be a difference, Any where else to look? Steve -- Steven Ellis - Bulletin.Net Inc - http://www.bulletin.net

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How do I reduce a disk size of a particular VM?
by Poh Yong Hwang 21 Sep '10

21 Sep '10

Hi, As per subject, is there a way to reduce diskspace for a VM. I have a VM with 200GB but would like to reduce the diskspace to 100GB. Please advise. Thanks! Yongsan

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Anyone booting CentOS 5.5 KVM host from flash?
by David Knierim 02 Sep '10

02 Sep '10

I am investigating building a live CD image to be used as KVM host and then putting that image on a USB key (to end up with a environment similar to ESXi). I see tools in in Fedora for both tasks, but I have not seen them in CentOS. Before I blaze a path, I was wondering if anyone has done this before.. Thanks for any feedback, David

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kvm, kvm_intel
by Lars Hecking 26 Aug '10

26 Aug '10

Which configuration or rc script is responsible for loading the kvm modules on CentOS 5.4/5.5? They interfere with vmware. --------------------------------------------------------------- This message and any attachments may contain Cypress (or its subsidiaries) confidential information. If it has been received in error, please advise the sender and immediately delete this message. ---------------------------------------------------------------

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Booting CentOS 5.5 (KVM) from a second disk
by Daniel Bareiro 24 Aug '10

24 Aug '10

Hi all! Doing some tests with CentOS 5.5 on a KVM virtual machine, after doing the installation, I added a second disk. But when trying to boot from it, I get the following error: --------------------------------------------------------------------- root (hd1,0) Error 21: Selected disk does not exist --------------------------------------------------------------------- The two disks are Virtio devices that are recognized when booting from the first disk: --------------------------------------------------------------------- [root@localhost ~]# fdisk -l /dev/vda Disco /dev/vda: 10.7 GB, 10737418240 bytes 255 heads, 63 sectors/track, 1305 cylinders Unidades = cilindros de 16065 * 512 = 8225280 bytes Disposit. Inicio Comienzo Fin Bloques Id Sistema /dev/vda1 * 1 1174 9430123+ fd Linux raid autodetect /dev/vda2 1175 1305 1052257+ fd Linux raid autodetect [root@localhost ~]# [root@localhost ~]# [root@localhost ~]# fdisk -l /dev/vdb Disco /dev/vdb: 10.7 GB, 10737418240 bytes 255 heads, 63 sectors/track, 1305 cylinders Unidades = cilindros de 16065 * 512 = 8225280 bytes Disposit. Inicio Comienzo Fin Bloques Id Sistema /dev/vdb1 * 1 1174 9430123+ fd Linux raid autodetect /dev/vdb2 1175 1305 1052257+ fd Linux raid autodetect --------------------------------------------------------------------- The idea of these tests is to set up software RAID1 on a running system, since, as I said in another thread, it seems that Anaconda does not support installation on degraded RAID. But I'm not sure if this is a problem of Virtio or that GRUB is not recognizing the second disk. I made sure to modify /boot/grub/device.map with the entry for the new disk: --------------------------------------------------------------------- [root@localhost grub]# cat /boot/grub/device.map # this device map was generated by anaconda (hd0) /dev/vda (hd1) /dev/vdb --------------------------------------------------------------------- And the reconfiguration of GRUB on both disks did not give problems: --------------------------------------------------------------------- [root@localhost grub]# grub --device-map=/boot/grub/device.map GNU GRUB version 0.97 (640K lower / 3072K upper memory) [ Minimal BASH-like line editing is supported. For the first word, TAB lists possible command completions. Anywhere else TAB lists the possible completions of a device/filename.] grub> root (hd0,0) root (hd0,0) Filesystem type is ext2fs, partition type 0xfd grub> setup (hd0) setup (hd0) Checking if "/boot/grub/stage1" exists... yes Checking if "/boot/grub/stage2" exists... yes Checking if "/boot/grub/e2fs_stage1_5" exists... yes Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 15 sectors are embedded. succeeded Running "install /boot/grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/boot/grub/stage2 /boot/grub/grub.conf"... succeeded Done. grub> root (hd1,0) root (hd1,0) Filesystem type is ext2fs, partition type 0xfd grub> setup (hd1) setup (hd1) Checking if "/boot/grub/stage1" exists... yes Checking if "/boot/grub/stage2" exists... yes Checking if "/boot/grub/e2fs_stage1_5" exists... yes Running "embed /boot/grub/e2fs_stage1_5 (hd1)"... 15 sectors are embedded. succeeded Running "install /boot/grub/stage1 (hd1) (hd1)1+15 p (hd1,0)/boot/grub/stage2 /boot/grub/grub.conf"... succeeded Done. grub> quit quit --------------------------------------------------------------------- Any idea what may be causing the problem? Thanks in advance for your replies. Regards, Daniel

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awful i/o performance on xen paravirtualized guest
by Fernando Gleiser 21 Aug '10

21 Aug '10

Hi. I'm testing a centos 5.4 xen PV guest on top of a centos 5.4 host. for some reason, the disk performance from the guest is awful. when I do an import , the io is fine for a while then climbs to 100% and stays there most of the time. at first I tougth it was because I was using file-backed disks, so deleted those and changed to LVM, but the situation did't improve. Here's an iostat output from within the DomU: Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util xvda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 xvda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 xvda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 xvdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 xvdc 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 xvdd 0.00 271.00 0.00 179.00 0.00 1800.00 20.11 1.99 11.11 5.59 100.00 dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-4 0.00 0.00 0.00 450.00 0.00 1800.00 8.00 4.93 10.93 2.22 100.00 the service time is a bit high but the and here from within the dom0: Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util cciss/c0d0 0.00 0.00 0.00 169.00 0.00 1640.00 19.41 2.00 11.74 5.94 100.40 cciss/c0d0p1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 cciss/c0d0p2 0.00 0.00 0.00 169.00 0.00 1640.00 19.41 2.00 11.74 5.94 100.40 dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 0.00 87.00 0.00 768.00 17.66 1.00 11.45 11.49 100.00 dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-4 0.00 0.00 0.00 82.00 0.00 856.00 20.88 1.00 12.05 12.24 100.40 a DB import takes almost 10 times longer than in the bare-metal server, even if the server I'm planing to virtualize is 4 years old and the guest is a brand new DL380 from HP. In the old server takes 4hs, in the new one takes 2 days. That's not surprising given the fact that the disk shows a peak throughput below 2Mb/s here's the vm config file: [root@xen2 xen]# cat vm-dbweb name = "vm-dbweb" uuid = "8560e33a-865e-cca5-725d-817de4972422" maxmem = 7168 memory = 7168 bootloader="/usr/bin/pygrub" vcpus = 2 on_poweroff = "destroy" on_reboot = "restart" on_crash = "restart" disk = [ "tap:aio:/var/lib/xen/images/vm-artweb.img,xvda,w", \ "tap:aio:/var/lib/xen/images/dbweb_home.img,xvdb,w", \ "phy:/dev/VolGroup00/dbweb_oradata,xvdc,w", \ "phy:/dev/VolGroup00/dbweb_oradata2,xvdd,w" ] vif = [ "mac=00:16:36:5a:4d:a1,bridge=xenbr0,script=vif-bridge" ] I'm pretty sure there is a way to get decent disk performance from a domU, and I must be screwing things up somewhere, I just don't find where :/ any help/pointers/tips for disk tuning would be greatly apreciated. Fer

1 0

Vmware Server 2 and KVM....
by Tom Bishop 17 Aug '10

17 Aug '10

I am finally starting to pull the plug on vmware 2 and want to start migrating to KVM, what I would like to know and I have searched but not found anything conclusive. Is it possible to run Vmware server 2 and KVM at the same time, I am running Centos 5.5 x64 on a 16 core 32g memory machine....the reason I would like to do this is that it would allow me to convert the vm's one at a time and do it in more of a phased approach, otherwise I may have to try to do it all at the same time....I dont have many VM's maybe 6 or 7 but would be nice if I could do them one at a time....Thanks in advance.... :)

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Jack Van Ham is out of the office.
by jack.vanham＠agfa.com 16 Aug '10

16 Aug '10

I will be out of the office starting 08/16/2010 and will not return until 08/20/2010. I will be out of the office (training) for the week of AUG 16 to AUG 20, 2010. I will check email as often as I can. For urgent matter, please call: 519-574-7707 (cell), and leave me a message if I do not answer, and I'll get back to you.

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IP aliases from a QEMU/KVM guest
by Mathieu Baudier 13 Aug '10

13 Aug '10

Hello, I'm trying to set up IP aliases within a QEMU/KVM guest on CentOS 5.5 x86_64, going through a bridged virtualized interface. The virtualized interface in the guest is configured as follow: # ifcfg-eth1 DEVICE=eth1 BOOTPROTO=none PEERDNS=yes GATEWAY=IP.OF.HOST.GATEWAY HWADDR=11:11:11:11:11:11 IPADDR=IP.OF.GUEST.ETH1 NETMASK=255.255.255.255 ONBOOT=yes ARP=yes USERCTL=no IPV6INIT=no # route-eth1 IP.OF.HOST.GATEWAY dev eth1 default via IP.OF.HOST.GATEWAY dev eth1 This is the configuration recommended by the provider (OVH) after a virtual MAC address has been allocated for IP.OF.GUEST.ETH1: http://help.ovh.com/BridgeClient It works fine for virtual interfaces added via libvirt/QEMU. But when I try to configure an IP alias on another IP address aliasing a virtualized interface, as per the instructions from http://help.ovh.co.uk/IpAlias (and after assigning it a virtual mac just like for eth1) : # ifcfg-eth1:1 DEVICE=eth1:1 BOOTPROTO=none PEERDNS=yes GATEWAY=IP.OF.HOST.GATEWAY HWADDR=22:22:22:22:22:22 IPADDR=IP.OF.GUEST.ETH1:1 NETMASK=255.255.255.255 ONBOOT=yes ARP=yes USERCTL=no IPV6INIT=no I get the following error when restarting the network: SIOCADDRT: Network is unreachable and IP.OF.GUEST.ETH1:1 is: - pingable from the same guest - not pingable from other guests by the same provider - not pingable from outside Setting BOOTPROTO=static or commenting out #GATEWAY=IP.OF.HOST.GATEWAY or setting: NETMASK=255.255.255.252 (the IP block was a /30, but I don't think that has something to do here) did not change the behavior. I'll be interested to hear from experiences with setting IP alias from within a guest. Maybe my problem is due to the configuration of the provider network and it is actually impossible to use IP aliases on virtualized interfaces. Any opinion/idea welcome! Mathieu

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IP based VirtualHost: IP aliases vs. additional virtual interfaces
by Mathieu Baudier 10 Aug '10

10 Aug '10

Hi, I have a virtualized infrastructure based on KVM/QEMU with CentOS 5.5 x86_64 hosts and guests, using bridge networking. I want to set up IP based VirtualHosts in Apache (because they will use SSL) and I have ordered an IP block. Now, in order to have the IPs available on some guests, I'm wondering whether I should: 1 - add additional virtual interfaces or 2 - set up IP aliases (eth0:1, etc.) in the guests I imagine that (1) would be faster and more efficient (but that's a guts feeling), and it feels cleaner. But with (2), I just need to restart the network in order to add new IPs (there won't be that many: like around 10 in the next few months), insteead of restarting the whole guest. Are there any best practices for adding IP-addresses to virtualized guests? Thanks in advance for your insights! Mathieu

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