Hot answers tagged kvm-virtualization
28
That benchmark is only comparing the speed of the native os to a single guest os. Hardly a real world test. I don't think I would put much weight on it. Most of the KVM camp argues that Xen requires too many interrupts and hops between kernel and user space but from most of the more real world benchmarks that I've seen that hasn't really been realized and ...
16
Having recently gone through the same song and dance with my own management ("VMWare is really expensive! Check out what OSS options there are out there.") I have some observations to share.
I/O performance does vary by hypervisor, though CPU performance is much less variant.
In general, 'thin' provisioning is a great way to dock I/O performance. Some ...
15
Flashcache, for those who haven't seen it before, is a method for extending the Linux block-cache with a SSD drive. It's cheaper than running a server with a half TB of RAM just for caching.
Will this even work?
It should. The Linux block-cache works by caching accessed blocks, not files. So long as you're not giving the KVM machines direct access to ...
15
Qemu:
QEmu is a complete and standalone software on it's own. You use it to emulate machines, it's very flexible and portable. Mainly it works by a special 'recompiler' that transforms binary code written for a given processor into another one (say, to run MIPS code on a PPC mac, or ARM in an x86 PC).
To emulate more than just the processor, Qemu ...
15
Xen supported virtualization types
Xen supports running two different
types of guests. Xen guests are often
called as domUs (unprivileged
domains). Both guest types (PV, HVM)
can be used at the same time on a
single Xen system.
Xen Paravirtualization (PV)
Paravirtualization is an efficient and
lightweight virtualization ...
13
Xen is an hypervisor that runs on metal (the pc / server) and then hosts virtual machines called domains.
A Xen PV domain is a paravirtualized domain, that means the operating system (usually we're talking linux here) has been modified to run under Xen, and there's no need to actually emulate hardware. This should be the most efficient way to go, ...
12
Honestly, I don't see what benefit you would get using any virtualization technology.
You are still using one server, there is no reduction in hardware use.
As you have only this one server, the possible benefit of being able to migrate virtual machines (maybe even while running) doesn't apply.
The amount of work necessary to keep the virt. servers ...
11
KVM has a much better snapshot capability than what's managed by libvirt; but it depends on qcow2 images. if you use them, just do a savevm <name> on the command console (blocked by libvirt) it won't create a new file, it's a snapshot inside the qcow2 file.
test it first, because some KVM versions have it broken.
11
RHEV is the stable version, while oVirt is upstream. Features from oVirt get merged into RHEV when stable and tested.
Consider Fedora and RHEL - Fedora is a rich distribution in terms of features and packages, but it's not supported commercially, has a short lifecycle, and is not geared towards stability. RHEL is based on Fedora, but it's code is tested and ...
10
There has been a good amount of press regarding the latest AMD processor offering, called Bulldozer. The "Server" version of this part isn't out yet, but the desktop offering is a great view into some of the potential problems of the new stuff.
As for the current generation of Server part, all in all the recommendation is fairly good at a generic level. ...
9
If you defined no CDROM when you created your virtual machine, you can attach the device even to a running domain (virtual machine) by running the following command:
virsh attach-disk testbed /dev/sr0 hdc --type cdrom
If you already defined a CDROM, but it pointed to an ISO image, in my experience, you can still run the same command. The hdcpart needs to ...
8
You're correct, standard ethernet cables won't work due to the wiring sequence - cisco uses what's called a "rollover cable" for their serial consoles. An example of the pin-out for rollover can be found here:
http://pinouts.ru/NetworkCables/rj45_rollover_pinout.shtml
It's as simple as pin 8 on one end is swapped to pin 1 on the other end, pin 7 to pin 2, ...
8
I've got 15 GB of free memory that can be used without having the processes swapped out.
No, you don't.
total used free shared buffers cached
Mem: 32094 31868 225 0 559 16175
You have 225MB of memory free.
KiB Swap: 1998844 total, 1113352 used, 885492 free, 16498252 ...
8
This is the forwarding delay for interfaces joining the bridge. It's how long it'll be before the interface will be able to do anything. . During this time the bridge will be discovering other bridges and checking that no loops are created. For a better description and the reason for it you need to read up on spanning tree protocol.
8
Ease of management is achieved by using libvirt which will present the same interface whether you use Xen or KVM. Stability is very much a function of the underlying distribution - Xen only works well with certain (generally older) kernels, whereas KVM is mainline and so gets fixes with every release.
8
The latest stable release for libvirt for Ubuntu is version 0.7.5, which doesn't have some newer features (i.e. script hooks and network filters) which make automatic network configuration easier. That said, here's how to enable port forwarding for libvirt 0.7.5 on Ubuntu 10.04 Lucid Lynx.
These iptables rules should do the trick:
iptables -t nat -I ...
7
We use Xen currently, but I think that in 2011 we will be migrating to KVM. There are some reasons why:
KVM development is more integrated with the Linux kernel than Xen's development.
KVM vms run as processes to the linux kernel. That has many implications, like scheduling, memory management and etc. That also permits KVM to do overcommit of memory (it's ...
7
Yes you can install the video hook driver on Vista, but you have to do it manually.
To improve speed, right click on the UltraVNC icon on the taskbar and select properties. Then tick the following boxes:
Poll Full Screen
Poll Foreground Window
Poll Window Under Cursor
System HookDll
If you are using the video hook driver, check if the Video Hook ...
7
In general, I leave HyperThreading ON for VM host servers (VMWare ESXi, KVM, HyperV, etc.). This applies to Intel Nehalem and newer CPUs (5500-series and greater). Additional threads available for scheduling multiple VMs.
You may also want to reevaluate the sizing of your guest systems. Typically, it's best to start small on the CPU allocation with virtual ...
7
The image will not shrink automatically, since when you delete files, you don't actually delete data (this is why undelete works). Qemu has a facility to shrink qcow2 images back, but what the utility does is really deduplicate the zeroes from the disk, leaving all other information intact. So the idea would be to:
Zero-fill the drive (dd if=/dev/zero ...
6
The optimal configuration is (usually) as follows:
On the host, set elevator=deadline
Use virtio and only virtio
use raw LVs whenever possible. Qcow2 gives overhead. Files on a FS also have overhead
in the VM use the elevator=noop
both in host and VM, use noatime,nodiratime in fstab wherever possible
Make sure the virtio drivers are up to date, especially ...
6
Haymaker beat me to it...
You don't say what Cisco device or what KVM, but chances are you want what Cisco calls a rollover cable:
Pin 1 on one end connects to Pin 8 on the other
Pin 2 Pin 7
Pin 3 Pin 6
Pin 4 Pin 5
etc.
Pin 8 Pin 1
This is basically a null-modem ...
6
When connected to the monitor via telnet, anything that you type will be interpreted as a command by the monitor itself. You can view the full list of commands in the QEMU Emulator User Documentation, one of which is quit (or q for short).
To disconnect the telnet session you need to first use the telnet escape key which is Ctrl-] and then you can type quit ...
6
I'll ask, how important is it that you specifically use KVM?
My preference for the type of solution you're inquiring about is to build around VMWare ESXi. You can build an all-in-one server running VMWare ESXi booting from flash media (SDHC, USB, CF) and leverage the DirectPath I/O (PCI-passthrough) available on current servers to present a SAS/SATA HBA to ...
6
install libguestfs:
# yum install libguestfs-tools
use guestfish to open the disk image:
# guestfish -a /path/to/diskimage.img
Welcome to guestfish, the libguestfs filesystem interactive shell for
editing virtual machine filesystems.
Type: 'help' for help on commands
'man' to read the manual
'quit' to quit the shell
<fs> run
...
6
Running BTRFS on the host for disk images (qcow2, etc) is a really bad idea. The style of disk writes to an image file is the worst IO pattern for btrfs, the tuning KVM page does not contain a lot of tips:
http://www.linux-kvm.org/page/Tuning_KVM
But on this one they are clear:
"Don't use the linux filesystem btrfs on the host for the image files. It will ...
6
The solution I used to circumvent this problem is:
First of all we will need to create an image to install the virtual machine into. Microsoft says 10 GB is the minimum, but I used 15 GB. Remember that this is not the final size of your virtual machine,once it is introduced into Nova Compute.
Create a raw image called windows.virtio:
kvm-img create -f raw ...
6
KVM provides full hardware virtualization, but you can use paravirtualized disk and network drivers (virtio). Most current Linux distributions will use them by default provided you've configured them when setting up the VM.
Since you expanded your question, I'll expand my answer.
In full hardware virtualization, every component of the virtual PC appears to ...
6
It's possible to get away with no graphics card at all, using only the console port (COM port), SSH, etc for administration. This is sufficient for most applications, it's still somewhat uncommon for VMs to "require" a graphics card. Certain situations do warrant passing a graphics card through to a VM however.
6
Those of the virtual machines that are totally idle with no services running
In reality, this does not happen; there are always services running on a *nix system:
syslog
systemd/udev
upstart
hald/dbus
cron/at
+any number of kernel threads
Expecting any combination of the above to yield a totally idle system is fantasy.
Besides that, the logic ...
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