Entries Tagged 'Virtualisation' ↓

Lucid libvirt

Lucid does not seem to work well with libvirt/kvm, there are several bugs that seem to be fixed in Maverick but not in Lucid.

From syslog:

error : qemuSetupCgroup:1955 : Unable to create cgroup for DOMAIN: No such file or directory
error : qemuRemoveCgroup:2045 : internal error Unable to find cgroup for DOMAIN#012

Re: [libvirt] FYI, “Unable to create cgroup for …”

This is a bug in systemd. It periodically scans all mounted cgroups
and deletes any directories which don’t contain any attached processes.
Needless to say this breaks libvirt, and possibly other apps, which
don’t expect 3rd parties to be deleting their directories.

https://bugzilla.redhat.com/show_bug.cgi?id=678555

Best solution for this that I’ve found on lucid is: Bug 696218 – Unable to create cgroup: No such file or directory

I was able to solve it by modifying the configuration in the file
/etc/libvirt/qemu.conf:

 cgroup_controllers = [ ]

setgid, setuid needed by /etc/apparmor.d/abstractions/libvirt-qemu

=== modified file 'apparmor.d/abstractions/libvirt-qemu'
--- apparmor.d/abstractions/libvirt-qemu 2010-04-30 15:33:20 +0000
+++ apparmor.d/abstractions/libvirt-qemu 2010-05-12 17:26:56 +0000
@@ -8,6 +8,8 @@
   capability dac_override,
   capability dac_read_search,
   capability chown,
+ capability setgid,
+ capability setuid,

Libvirt/kvm permissions/ownership issue on upgrade from Karmic to Lucid and error: operation failed: failed to retrieve chardev info in qemu with ‘indev’

libvirtError: internal error unable to start guest: libvir: QEMU
error : cannot set ownership

or

 error: operation failed: failed to retrieve chardev info in qemu with 'indev'

Add the following to /etc/libvirt/qemu.conf:

# The user ID for QEMU processes run by the system instance
#user = "libvirt-qemu"
user = "root"

# The group ID for QEMU processes run by the system instance
group = "kvm"

map serial port throws “chardev: opening backend “tty” failed”

There seems to be a problem with the apparmor profile of libvirt (see bug #54579). After adding the line to /etc/apparmor.d/abstractions/libvirt-qemu and reloading the profile it worked for me.

/dev/ttyS* rw,

Few other links:

kvm vs qemu-kvm vs kvm-kmod

Ubuntu recently change their package names for kvm.  This comment posted on qemu-0.11.0 Released provides an explanation:

qemu-kvm includes features and fixes from upstream qemu and so takes its naming scheme from upstream qemu. You can think of it as qemu optimized for kvm. Note too that qemu-kvm does not include the kernel module but only the userspace and considered to be stable.

kvm-xx on the other hand is the development branch of kvm and not considered to be stable. It’s naming scheme is arbitrary and it also takes features from upstream qemu.

kvm-kmod is different to kvm-xx. You can think of kvm-kmod as a subset of the kvm-xx. KVM-xx = userspace + kernel where kvm-kmod is the kernel part of it and qemu-kvm is the userspace part (the guest process itself). You can apply the kvm-kmod to any distro version or linux version.. it’s just the kernel driver. However, without the userspace part, you can’t do much with it.

kvm disk performance with different backends

Here  some results from testing I did in August 2009 on  KVM with the three different disk image drivers. First a single disk system running Ubuntu x64 9.04:

Continue reading →

50% Performance Boost for Nehalem’s over Harpertown

From the vmware blog:

Conclusion

A 1vCPU Xeon X5500 series based Exchange Server VM can support 50% more users per core than a 2vCPU VM based on previous generation processors while maintaining the same level of performance in terms of Sendmail latency.  This is accomplished while the VM’s CPU utilization remains below 50%, allowing plenty of capacity for peaks in workload and making an FT VM practical for use with Exchange Server 2007.

linux-image-virtual with ESX

According to this thread, if you need to use the linux-image-virtual package on ubuntu then it only supports the “bus logic” scsi controller with ESX.

ESX Console via SSH

PuTTY
Image via Wikipedia

Need to access the ESX console with the Virtual Infrastructure Client in some remote location where your VPN does not work.  Forward ports 443, 902 and 903 with putty.  Port specifics for ESX can be found on page 179 of the ESX Server Config guide.

In my case I additionally need to forward from a boundary machine:
ssh -L 8443:localhost:443 -L 8902:localhost:902 -L 8903:localhost:903 node2

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Load average and Vmware Server Hang Fix

Couple useful articles from Andy Millar.

  • Concise and clear explaination of linux load averages.
  • Bug fix suggestion for VMware server which can hang on installation. Remove the floppy device. I’ve got another issue where a linux vm on vmware server hangs on startup and I’ll have to try this.

VM Template best practices (Windows)…

Installing Windows XP

Image by Trey Piepmeier via Flickr

Useful article on template windows vmware images. One point of great note:

As a result of point (4), your OS disk is now perfectly aligned with the storage layer below it, increasing disk I/O performance. This is actually a server OS problem that applies to all of Microsoft’s pre-Windows Server 2008 server operating sustems, and Windows XP. A simple explanation is that systems like to write data in 64k chunks onto disks with 64k sectors. However, they create their very first chunk at only 63k in size. That means every subsequent chuck writes at least 1k to the previous sector, resulting in every read and write going to two sectors and resulting in two I/Os per operation instead of just one I/O. This is what you’ve just corrected in (4).

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Discussion of Clouds

Nice clear video presentation about cloud computing.

Redhat and KVM

Redhat has acquired Qumranet the developers of KVM. Will be interesting to see how this plays out in the Linux virtualisation world.

I haven’t tried KVM yet as I’ve been too busy and Xen is more mature – but many of the accounts I’ve read seem to indicate that for Linux its performance is very good maybe better in some cases than Xen. Management is another issue, but that is just a matter of time and development enegry.

From lwn.


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