virt October 2009

virt@lists.centos.org

20 participants
17 discussions

High CPU usage when running a CentOS guest in VirtualBox
by Sagi Bashari 16 Nov '09

16 Nov '09

Hi, I am running CentOS 5.3 32bit as a VirtualBox 3.0.0 guest running on Windows XP. The Windows host CPU usage is constantly at 50% although the CentOS guest is completely idle (i.e. 0.00 load average). I know this is a common problem related to the 1000Hz frequency that the CentOS kernel runs at. With previous versions of CentOS, I used the kernel-vm package [1] and it solved my problem. However, according to the README [2] this isn't necessary as of CentOS 5.3 and therefore these packages are not maintained anymore (the latest released kernel-vm is 2.6.18-92.1.22). >From what I understand, as of CentOS 5.3 it is possible to use the "divider=10 clocksource=acpi_pm" to reduce the frequency to 100Hz. I tried this setting, and it made no difference at all. I also tried to install the VirtualBox guest extensions, and still, the host CPU never goes below 50%. Is there any way to solve this issue without resorting to a custom kernel build? Thanks, Sagi [1] http://people.centos.org/tru/kernel-vm/ [2] http://people.centos.org/tru/kernel-vm/readme.txt

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Domain0 with Kernel 2.6.18-92.1.22.el5xen fails to boot Guests with Kernel 2.6.18-164.el5xen
by Devraj Mukherjee 09 Nov '09

09 Nov '09

Hi all, I am in a bit of a fix here, I have several Guests paravirtualized running on a Dom0 that is currently running the 2.6.18-92.1.22.el5xen Kernel. All my guests (administered by different people) have subsequently been updated to later versions of the kernel (namely 2.6.18-164.el5xen or 2.6.18-128.4.1.el5xen). Ones that are still running are using the Kernel 2.6.18-128.4.1.el5xen while Dom0 is still booted up into 2.6.18-92.1.22.el5xen I restarted a Guest that's now trying to boot with the 2.6.18-164.el5xen Kernel and it spits out messages like XENBUS: Waiting for devices to initialise: 295s...290s... and eventually reboots. If I try and interrupt the boot and choose a previous version of the Kernel on the Guest, it says the following and fails to boot. The guests use a single disk image that has the SWAP and Root partitions. Is this happening because the version of the kernel on the Dom0 is way too old for guests to boot? I am just a bit hesitant in rebooting my server for the new kernel to take effect unless I am sure :) device-mapper: dm-raid45: initialized v0.2429 Scanning and configuring dmraid supported devices Scanning logical volumes Reading all physical volumes. This may take a while... Activating logical volumes Volume group "VolGroup00" not found Creating root device. Mounting root filesystem. mount: could not find filesystem '/dev/root' Setting up other filesystems. Setting up new root fs setuproot: moving /dev failed: No such file or directory no fstab.sys, mounting internal defaults setuproot: error mounting /proc: No such file or directory setuproot: error mounting /sys: No such file or directory Switching to new root and running init. unmounting old /dev unmounting old /proc unmounting old /sys switchroot: mount failed: No such file or directory Kernel panic - not syncing: Attempted to kill init! -- "The secret impresses no-one, the trick you use it for is everything" - Alfred Borden (The Prestiege)

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SATA vs RAID5 vs VMware
by Philip Gwyn 03 Nov '09

03 Nov '09

Hello, I have strange behaviour on a server that I can't get a handle on. I have a reasonably powerful server running VMware server 1.0.4-56528. It has a RAID5 build with mdadm on 5 SATA drives. Masses of ram and 2 XEON CPUs. But it stutters. Example : fire up vi, press and keep finger on i. After filling 2-3 lines, the display is stopped for 2-12 seconds. Then they continue. This happens even on the host OS, at the console. Host system running CentOS 5.2 x86-64: CPU : 2x Xeon E5430 @ 2.66GHz RAM : 24GB Mobo : DSBV-DX HD : 5 x SATA ST3750330AS 750GB in RAID5 There are 5 VMs, detailed at http://www.awale.qc.ca/vmware/stj1.txt to make this mail shorter. Seems to me this system should be more then adequate to handle the load. This is what vmstat on the host looks like when the server is "unhappy" : http://www.awale.qc.ca/vmware/vmstat.txt Spending a lot of time in 'wa', but 'bo' and 'bi' are miniscule. The problem seems like a disk problem. I grow to suspect that SATA isn't ready for the big time. I also grow to dislike RAID5. Questions : - Anyone have a clue or other on how to track down my bottle neck? - SATA NCQ is limited to 15 queue depth. Is this per-SATA-port or per-SATA-chip? Or does this question make no sense? - I realise there are more recent versions of CentOS out. Are there specific items in the changelogs that would affect my problem? Thank you for any help, -Philip

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Xen network problem
by Ken Bass 30 Oct '09

30 Oct '09

I have a machine with 8 CPU's (2 quad xeons). (Centos 5.4 currently). Currently, I am running 2 domUs. One with 4 CPUs and another with 2. 2 remain unused. I am using routed networking. On the one machine with 4 CPU's, there is a cronjob at 4am which utilizes the CPU/disk pretty heavily. It is rebuilds a mailing list archive (using MHonarc) and rebuilds a search engine index (swish-e). I dont think it uses more than 1 CPU though because the index rebuilding is not multi threaded, as far as I know. This cron runs at 4am each day and takes about 7 minutes. My ISP is telling me that their alarms are going off because they cannot ping my server between 4am and 4:07am. It sounds like the domU is impacting the overall Xen performance. Is there anything I can do to tune this? It kinda defeats the whole Xen virtualization concept if a single CPU messes up the network. I am going to try to add a 'nice' to the crontab for the 4am job, but still, something doesn't seem correct. Any suggestions would be much appreciated. Thanks!

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Xen vs. KVM console
by Dennis J. 26 Oct '09

26 Oct '09

Hi, I'm trying to get the console support in KVM working as well as on Xen but right now I'm stuck. I followed these instructions: http://prefetch.net/blog/index.php/2009/06/17/redirecting-the-centos-and-fe… This works out fairly well except that I cannot watch the bootup of the machine in the vnc console anymore only on the serial console and I also don't get any output on the vnc console on shutdown. Is there a way to configure the serial console in such a way that I don't lose a part of the functionality of the vnc console? Regards, Dennis

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Re: [CentOS-virt] Move Windows within an LV to another pv safely
by Christopher G. Stach II 26 Oct '09

26 Oct '09

----- "Ben M." <centos(a)rivint.com> wrote: > What a mess that turned out to be. Hey, maybe it was your "awesome > numbering" <ducking and running>. jk, probably because I forgot to > take > some meds today or something. Measure twice. Cut once. :) > Oh, the dd quit on me before complete. Is it okay making the target lv > bigger than the source when I try it again or does it have to be > exact? > I need some extra disk space in that xen vm too. You can make it larger if you want. The partition table copied from the source will only have the original size allocated. Did you allocate the new LV with the same number of extents on a VG with the same extent size? It should work perfectly, if so. -- Christopher G. Stach II

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Re: [CentOS-virt] Move Windows within an LV to another pv safely
by Christopher G. Stach II 26 Oct '09

26 Oct '09

----- "Ben M." <centos(a)rivint.com> wrote: > Does this appear to be a sound procedure? I have one inline question. I read your version of the procedure and it looks like you want to skip the pvmove. That's fine, but it means more downtime (an unreliable estimate is one minuted per GB). In that case, you don't even need the snapshot. You won't need a point in time copy if you are copying from a stable source. > 1. Shutdown domU source (source lvname = win2k8-source) which is never > file mounted in Xen dom0, just "lvm'd". Yeah, just turning off the guest and making sure it doesn't have the ``o'' flag set in the ``lvs'' output is enough. I hope that nothing else had it open (for writing) while your guest was running. :) > 2. snapshot source win2k8-source to win2k8-snapshot > [How long do I wait before bringing DomU source back up? Is there in > indication when it is done? It is approx. 50gig] A few milliseconds. It will return almost immediately. > 3. Bring up domU (Is this necessary if seeking accurate data state, > would rather keep offline on a weekend dayrather than lose data > entries.) The snapshot won't change. It's not necessary if you don't need your guest to be up. In fact, you can skip the whole snapshot bit if you don't care about downtime for your guest. Just dd from win2k8-source. You can't perform this step if you aren't going to use pvmove. Your source will change and your snapshot will be out of date. You would lose all of your changes between the snapshot and when you reboot the guest the second time. > 4. Create identical lv extent space (win3k8-target) on target pv/vg Yes, but win2k8-target. :) Since you are copying to a new VG, you can just keep the LV name the same. > 5. dd if=/dev/vgsnapshotsource/win2k8-snapshot > of=/dev/vgtarget/win2k8-target Yes, but you can specify a larger block size and it will take less time. I personally just default to using bs=1048576 for most things, even if it's not ideal. > 6. Shutdown DomU, change xen win2k8-source domU conf file phy: > reference to win2k8-target Nope. Keep it the same. You don't want to run from the snapshot or the backup copy, unless you're skipping the pvmove. If you are, you want to change the VG and/or LV name to the non-backup copy. > 6a. Drop snapshot, rename source lv to win2k8-old If you were going with pvmove, you would perform that after this step. > 7. Start "new" domU. > 8. test extensively, if works, run for few a day or two. Keep *-old as > fallback for a week or so. Then move to an archive using dd. So, we have two possible procedures intermingled here. The major differences are Procedure A (lots of downtime) and Procedure B (minimal downtime). Procedure A ~~~~~~~~~~~ 1. Create target LV with geometry identical to source LV geometry 2. Stop guest. 3. dd 4. Modify guest configuration to point to target LV 5. Start guest This is the procedure to use if simplicity is desired. As a perk, your source LV becomes your backup. Procedure B ~~~~~~~~~~~ 1. Create backup LV with geometry identical to source LV geometry 2. Stop guest. 3. Create snapshot of source LV 4. Start guest 5. dd from snapshot of source LV to backup LV 6. Drop snapshot of source LV 7. vgextend source VG with additional PV 7. pvmove source LV to additional PV (opt) 8. vgsplit [source VG into additional VG with additional PV] (opt) 9. Modify guest configuration [to point to source LV on additional VG] Procedure B can be different for Linux guests in that, depending upon your guest filesystem choices (ext3 journal, in particular) and site specific caching issues, step 2 could be "Pause guest" and step 4 would then be "Resume guest". Depending upon how you handle your PVs and VGs in the optional 8 and 9 steps, you may need to shut down your guest(s). Your desire to have one VG per PV will probably necessitate that being done eventually. -- Christopher G. Stach II

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Need info on vnet mapping to guests
by Neil Aggarwal 25 Oct '09

25 Oct '09

Hello: I have a host running two KVM guests. The guests use br0 and each has a static IP address. I am trying to figure out if there is a way to use snmpd on the host to measure the traffic usage of the guests. I do not want to require anything running on the guests since I do not control them. Looking at netstat -in on the host, I see this info: Kernel Interface table Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg br0 1500 0 237609 0 0 0 13615 0 0 0 BMRU eth0 1500 0 967594 0 0 0 354576 0 0 0 BMRU lo 16436 0 63 0 0 0 63 0 0 0 LRU virbr0 1500 0 0 0 0 0 32 0 0 0 BMRU vnet0 1500 0 29802 0 0 0 306940 0 0 0 BMRU vnet1 1500 0 311556 0 0 0 789331 0 0 0 BMRU Looking at the firewall logs for packets that hit the firewall, I see that vnet1 is connected to guestA and vnet0 is connected to guestB. Is there a better way to determine which vnet is connected to which guest? Also, does the mapping change when I stop and start guests or reboot the host? Thanks, Neil -- Neil Aggarwal, (281)846-8957, www.JAMMConsulting.com Will your e-commerce site go offline if you have a DB server failure, fiber cut, flood, fire, or other disaster? If so, ask about our geographically redundant database system.

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Sending function key like F12 to a booting cd
by Torkil Zachariassen 21 Oct '09

21 Oct '09

Under Xen I am booting a virtual server from a recovery CD-Rom (actually a iso image) When the cd boots in the console window I have to send the single key "F12" to the window within 10 seconds from start, otherwise it will try to boot from harddisk. Pressing F12 in the console window does not work - and I tried sdl as well as vnc. I can send various Ctrl+Alt-combinations using the menu item "Send key" but not Fn keys. Does anyone know how to send F12 or other function keys to a booting cd ? ...torkil... on centos 5.3, xen-3.0.3 and virt-manager 0.5.3.

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VNC not connecting
by Neil Aggarwal 21 Oct '09

21 Oct '09

Hello all: I am trying to install CentOS 5.4 as a KVM guest. The host is running CentOS 5.4 and does not have X installed. I used ssh to connect to the host and ran this command (I formatted it for readability, it is all on one line): virt-install -n jamm12e -r 1024 --vcpus=1 --check-cpu --os-type=linux --os-variant=rhel5 --hvm --accelerate --cdrom=/tmp/CentOS-5.4-x86_64-netinstall.iso -f /usr/local/virt/jamm12e.img -s 20 -b br0 --vnc --vncport=5903 When I do that, I get this error: (virt-viewer:3083): Gtk-WARNING **: cannot open display: Domain installation still in progress. You can reconnect to the console to complete the installation process. I did not expect the installation to try connect to the display since I told it to use VNC. Next, I tried to connect TightVNC viewer from my Windows XP laptop. I entered 192.168.2.200:3 as the server and tried to connect, but that failed. Did I miss something in the VNC configuration? I don't see any other parameters to use. Thanks, Neil -- Neil Aggarwal, (281)846-8957, www.JAMMConsulting.com Will your e-commerce site go offline if you have a DB server failure, fiber cut, flood, fire, or other disaster? If so, ask about our geographically redundant database system.

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virt October 2009