an iso image as a parameter to Qemu, and the OS running in the emulated computer
will see a real CDROM inserted in a CD drive.
-Qemu can emulates a great variety of hardware from ARM to Sparc, but {pve} is
+Qemu can emulate a great variety of hardware from ARM to Sparc, but {pve} is
only concerned with 32 and 64 bits PC clone emulation, since it represents the
overwhelming majority of server hardware. The emulation of PC clones is also one
of the fastest due to the availability of processor extensions which greatly
NOTE: You may sometimes encounter the term _KVM_ (Kernel-based Virtual Machine).
It means that Qemu is running with the support of the virtualization processor
extensions, via the Linux kvm module. In the context of {pve} _Qemu_ and
-_KVM_ can be use interchangeably as Qemu in {pve} will always try to load the kvm
+_KVM_ can be used interchangeably as Qemu in {pve} will always try to load the kvm
module.
Qemu inside {pve} runs as a root process, since this is required to access block
the guest OS recognizes it is running inside Qemu and cooperates with the
hypervisor.
-Qemu relies on the virtio virtualization standard, and is thus able to presente
+Qemu relies on the virtio virtualization standard, and is thus able to present
paravirtualized virtio devices, which includes a paravirtualized generic disk
controller, a paravirtualized network card, a paravirtualized serial port,
a paravirtualized SCSI controller, etc ...
Qemu can emulate a number of storage controllers:
* the *IDE* controller, has a design which goes back to the 1984 PC/AT disk
-controller. Even if this controller has been superseded by more more designs,
-each and every OS you can think has support for it, making it a great choice
+controller. Even if this controller has been superseded by recent designs,
+each and every OS you can think of has support for it, making it a great choice
if you want to run an OS released before 2003. You can connect up to 4 devices
on this controller.
When selecting _VirtIO SCSI single_ Qemu will create a new controller for
each disk, instead of adding all disks to the same controller.
-* The *Virtio* controller, also called virtio-blk to distinguish from
-the VirtIO SCSI controller, is an older type of paravirtualized controller
-which has been superseded in features by the Virtio SCSI Controller.
+* The *VirtIO Block* controller, often just called VirtIO or virtio-blk,
+is an older type of paravirtualized controller. It has been superseded by the
+VirtIO SCSI Controller, in terms of features.
[thumbnail="gui-create-vm-hard-disk.png"]
On each controller you attach a number of emulated hard disks, which are backed
thin provisioning of the disk image.
* the *raw disk image* is a bit-to-bit image of a hard disk, similar to what
you would get when executing the `dd` command on a block device in Linux. This
- format do not support thin provisioning or snapshotting by itself, requiring
- cooperation from the storage layer for these tasks. It is however 10% faster
- than the *QEMU image format*. footnote:[See this benchmark for details
+ format does not support thin provisioning or snapshots by itself, requiring
+ cooperation from the storage layer for these tasks. It may, however, be up to
+ 10% faster than the *QEMU image format*. footnote:[See this benchmark for details
http://events.linuxfoundation.org/sites/events/files/slides/CloudOpen2013_Khoa_Huynh_v3.pdf]
* the *VMware image format* only makes sense if you intend to import/export the
disk image to other hypervisors.
If you want the {pve} backup manager to skip a disk when doing a backup of a VM,
you can set the *No backup* option on that disk.
+If you want the {pve} storage replication mechanism to skip a disk when starting
+ a replication job, you can set the *Skip replication* option on that disk.
+As of {pve} 5.0, replication requires the disk images to be on a storage of type
+`zfspool`, so adding a disk image to other storages when the VM has replication
+configured requires to skip replication for this disk image.
+
If your storage supports _thin provisioning_ (see the storage chapter in the
{pve} guide), and your VM has a *SCSI* controller you can activate the *Discard*
option on the hard disks connected to that controller. With *Discard* enabled,
then shrink the disk image accordingly.
.IO Thread
-The option *IO Thread* can only be used when using a disk with the
+The option *IO Thread* can only be used when using a disk with the
*VirtIO* controller, or with the *SCSI* controller, when the emulated controller
type is *VirtIO SCSI single*.
With this enabled, Qemu creates one I/O thread per storage controller,
-instead of a single thread for all I/O, so it increases performance when
+instead of a single thread for all I/O, so it increases performance when
multiple disks are used and each disk has its own storage controller.
Note that backups do not currently work with *IO Thread* enabled.
This CPU can then contain one or many *cores*, which are independent
processing units. Whether you have a single CPU socket with 4 cores, or two CPU
sockets with two cores is mostly irrelevant from a performance point of view.
-However some software is licensed depending on the number of sockets you have in
-your machine, in that case it makes sense to set the number of of sockets to
-what the license allows you, and increase the number of cores.
+However some software licenses depend on the number of sockets a machine has,
+in that case it makes sense to set the number of sockets to what the license
+allows you.
Increasing the number of virtual cpus (cores and sockets) will usually provide a
performance improvement though that is heavily dependent on the use of the VM.
execution on the host system. If you're not sure about the workload of your VM,
it is usually a safe bet to set the number of *Total cores* to 2.
-NOTE: It is perfectly safe to set the _overall_ number of total cores in all
-your VMs to be greater than the number of of cores you have on your server (ie.
-4 VMs with each 4 Total cores running in a 8 core machine is OK) In that case
-the host system will balance the Qemu execution threads between your server
-cores just like if you were running a standard multithreaded application.
-However {pve} will prevent you to allocate on a _single_ machine more vcpus than
-physically available, as this will only bring the performance down due to the
-cost of context switches.
+NOTE: It is perfectly safe if the _overall_ number of cores of all your VMs
+is greater than the number of cores on the server (e.g., 4 VMs with each 4
+cores on a machine with only 8 cores). In that case the host system will
+balance the Qemu execution threads between your server cores, just like if you
+were running a standard multithreaded application. However, {pve} will prevent
+you from assigning more virtual CPU cores than physically available, as this will
+only bring the performance down due to the cost of context switches.
+
+[[qm_cpu_resource_limits]]
+Resource Limits
+^^^^^^^^^^^^^^^
+
+In addition to the number of virtual cores, you can configure how much resources
+a VM can get in relation to the host CPU time and also in relation to other
+VMs.
+With the *cpulimit* (`Host CPU Time') option you can limit how much CPU time the
+whole VM can use on the host. It is a floating point value representing CPU
+time in percent, so `1.0` is equal to `100%`, `2.5` to `250%` and so on. If a
+single process would fully use one single core it would have `100%` CPU Time
+usage. If a VM with four cores utilizes all its cores fully it would
+theoretically use `400%`. In reality the usage may be even a bit higher as Qemu
+can have additional threads for VM peripherals besides the vCPU core ones.
+This setting can be useful if a VM should have multiple vCPUs, as it runs a few
+processes in parallel, but the VM as a whole should not be able to run all
+vCPUs at 100% at the same time. Using a specific example: lets say we have a VM
+which would profit from having 8 vCPUs, but at no time all of those 8 cores
+should run at full load - as this would make the server so overloaded that
+other VMs and CTs would get to less CPU. So, we set the *cpulimit* limit to
+`4.0` (=400%). If all cores do the same heavy work they would all get 50% of a
+real host cores CPU time. But, if only 4 would do work they could still get
+almost 100% of a real core each.
+
+NOTE: VMs can, depending on their configuration, use additional threads e.g.,
+for networking or IO operations but also live migration. Thus a VM can show up
+to use more CPU time than just its virtual CPUs could use. To ensure that a VM
+never uses more CPU time than virtual CPUs assigned set the *cpulimit* setting
+to the same value as the total core count.
+
+The second CPU resource limiting setting, *cpuunits* (nowadays often called CPU
+shares or CPU weight), controls how much CPU time a VM gets in regards to other
+VMs running. It is a relative weight which defaults to `1024`, if you increase
+this for a VM it will be prioritized by the scheduler in comparison to other
+VMs with lower weight. E.g., if VM 100 has set the default 1024 and VM 200 was
+changed to `2048`, the latter VM 200 would receive twice the CPU bandwidth than
+the first VM 100.
+
+For more information see `man systemd.resource-control`, here `CPUQuota`
+corresponds to `cpulimit` and `CPUShares` corresponds to our `cpuunits`
+setting, visit its Notes section for references and implementation details.
+
+CPU Type
+^^^^^^^^
Qemu can emulate a number different of *CPU types* from 486 to the latest Xeon
processors. Each new processor generation adds new features, like hardware
but is guaranteed to work everywhere.
In short, if you care about live migration and moving VMs between nodes, leave
-the kvm64 default. If you don’t care about live migration, set the CPU type to
-host, as in theory this will give your guests maximum performance.
-
-You can also optionally emulate a *NUMA* architecture in your VMs. The basics of
-the NUMA architecture mean that instead of having a global memory pool available
-to all your cores, the memory is spread into local banks close to each socket.
+the kvm64 default. If you don’t care about live migration or have a homogeneous
+cluster where all nodes have the same CPU, set the CPU type to host, as in
+theory this will give your guests maximum performance.
+
+NUMA
+^^^^
+You can also optionally emulate a *NUMA*
+footnote:[https://en.wikipedia.org/wiki/Non-uniform_memory_access] architecture
+in your VMs. The basics of the NUMA architecture mean that instead of having a
+global memory pool available to all your cores, the memory is spread into local
+banks close to each socket.
This can bring speed improvements as the memory bus is not a bottleneck
anymore. If your system has a NUMA architecture footnote:[if the command
`numactl --hardware | grep available` returns more than one node, then your host
system has a NUMA architecture] we recommend to activate the option, as this
-will allow proper distribution of the VM resources on the host system. This
-option is also required in {pve} to allow hotplugging of cores and RAM to a VM.
+will allow proper distribution of the VM resources on the host system.
+This option is also required to hot-plug cores or RAM in a VM.
If the NUMA option is used, it is recommended to set the number of sockets to
the number of sockets of the host system.
+vCPU hot-plug
+^^^^^^^^^^^^^
+
+Modern operating systems introduced the capability to hot-plug and, to a
+certain extent, hot-unplug CPUs in a running systems. Virtualisation allows us
+to avoid a lot of the (physical) problems real hardware can cause in such
+scenarios.
+Still, this is a rather new and complicated feature, so its use should be
+restricted to cases where its absolutely needed. Most of the functionality can
+be replicated with other, well tested and less complicated, features, see
+xref:qm_cpu_resource_limits[Resource Limits].
+
+In {pve} the maximal number of plugged CPUs is always `cores * sockets`.
+To start a VM with less than this total core count of CPUs you may use the
+*vpus* setting, it denotes how many vCPUs should be plugged in at VM start.
+
+Currently only this feature is only supported on Linux, a kernel newer than 3.10
+is needed, a kernel newer than 4.7 is recommended.
+
+You can use a udev rule as follow to automatically set new CPUs as online in
+the guest:
+
+----
+SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1"
+----
+
+Save this under /etc/udev/rules.d/ as a file ending in `.rules`.
+
+Note: CPU hot-remove is machine dependent and requires guest cooperation.
+The deletion command does not guarantee CPU removal to actually happen,
+typically it's a request forwarded to guest using target dependent mechanism,
+e.g., ACPI on x86/amd64.
+
[[qm_memory]]
Memory
For each VM you have the option to set a fixed size memory or asking
{pve} to dynamically allocate memory based on the current RAM usage of the
-host.
+host.
.Fixed Memory Allocation
[thumbnail="gui-create-vm-memory-fixed.png"]
VM, because it delivers useful information such as how much memory the guest
really uses.
In general, you should leave *ballooning* enabled, but if you want to disable
-it (e.g. for debugging porpuses), simply uncheck
+it (e.g. for debugging purposes), simply uncheck
*Ballooning* or set
balloon: 0
When multiple VMs use the autoallocate facility, it is possible to set a
*Shares* coefficient which indicates the relative amount of the free host memory
-that each VM shoud take. Suppose for instance you have four VMs, three of them
+that each VM should take. Suppose for instance you have four VMs, three of them
running a HTTP server and the last one is a database server. To cache more
database blocks in the database server RAM, you would like to prioritize the
database VM when spare RAM is available. For this you assign a Shares property
of 3000 to the database VM, leaving the other VMs to the Shares default setting
-of 1000. The host server has 32GB of RAM, and is curring using 16GB, leaving 32
+of 1000. The host server has 32GB of RAM, and is currently using 16GB, leaving 32
* 80/100 - 16 = 9GB RAM to be allocated to the VMs. The database VM will get 9 *
3000 / (3000 + 1000 + 1000 + 1000) = 4.5 GB extra RAM and each HTTP server will
get 1/5 GB.
All Linux distributions released after 2010 have the balloon kernel driver
included. For Windows OSes, the balloon driver needs to be added manually and can
incur a slowdown of the guest, so we don't recommend using it on critical
-systems.
+systems.
// see https://forum.proxmox.com/threads/solved-hyper-threading-vs-no-hyper-threading-fixed-vs-variable-memory.20265/
-When allocating RAMs to your VMs, a good rule of thumb is always to leave 1GB
+When allocating RAM to your VMs, a good rule of thumb is always to leave 1GB
of RAM available to the host.
performance. Like all VirtIO devices, the guest OS should have the proper driver
installed.
* the *Realtek 8139* emulates an older 100 MB/s network card, and should
-only be used when emulating older operating systems ( released before 2002 )
+only be used when emulating older operating systems ( released before 2002 )
* the *vmxnet3* is another paravirtualized device, which should only be used
when importing a VM from another hypervisor.
{pve} will generate for each NIC a random *MAC address*, so that your VM is
addressable on Ethernet networks.
-The NIC you added to the VM can follow one of two differents models:
+The NIC you added to the VM can follow one of two different models:
* in the default *Bridged mode* each virtual NIC is backed on the host by a
_tap device_, ( a software loopback device simulating an Ethernet NIC ). This
tap device is added to a bridge, by default vmbr0 in {pve}. In this mode, VMs
have direct access to the Ethernet LAN on which the host is located.
* in the alternative *NAT mode*, each virtual NIC will only communicate with
-the Qemu user networking stack, where a builting router and DHCP server can
-provide network access. This built-in DHCP will serve adresses in the private
+the Qemu user networking stack, where a built-in router and DHCP server can
+provide network access. This built-in DHCP will serve addresses in the private
10.0.2.0/24 range. The NAT mode is much slower than the bridged mode, and
should only be used for testing.
If you are using the VirtIO driver, you can optionally activate the
*Multiqueue* option. This option allows the guest OS to process networking
packets using multiple virtual CPUs, providing an increase in the total number
-of packets transfered.
+of packets transferred.
//http://blog.vmsplice.net/2011/09/qemu-internals-vhost-architecture.html
When using the VirtIO driver with {pve}, each NIC network queue is passed to the
When using Multiqueue, it is recommended to set it to a value equal
to the number of Total Cores of your guest. You also need to set in
the VM the number of multi-purpose channels on each VirtIO NIC with the ethtool
-command:
+command:
-`ethtool -L eth0 combined X`
+`ethtool -L ens1 combined X`
where X is the number of the number of vcpus of the VM.
as a router, reverse proxy or a busy HTTP server doing long polling.
+[[qm_usb_passthrough]]
USB Passthrough
~~~~~~~~~~~~~~~
There are two different types of USB passthrough devices:
-* Host USB passtrough
+* Host USB passthrough
* SPICE USB passthrough
Host USB passthrough works by giving a VM a USB device of the host.
If a device is present in a VM configuration when the VM starts up,
but the device is not present in the host, the VM can boot without problems.
-As soon as the device/port ist available in the host, it gets passed through.
+As soon as the device/port is available in the host, it gets passed through.
-WARNING: Using this kind of USB passthrough, means that you cannot move
+WARNING: Using this kind of USB passthrough means that you cannot move
a VM online to another host, since the hardware is only available
on the host the VM is currently residing.
There are, however, some scenarios in which a BIOS is not a good firmware
to boot from, e.g. if you want to do VGA passthrough. footnote:[Alex Williamson has a very good blog entry about this.
http://vfio.blogspot.co.at/2014/08/primary-graphics-assignment-without-vga.html]
-In such cases, you should rather use *OVMF*, which is an open-source UEFI implemenation. footnote:[See the OVMF Project http://www.tianocore.org/ovmf/]
+In such cases, you should rather use *OVMF*, which is an open-source UEFI implementation. footnote:[See the OVMF Project http://www.tianocore.org/ovmf/]
If you want to use OVMF, there are several things to consider:
shutdown request, wait 60s for the machine to be offline, and if after 60s
the machine is still online will notify that the shutdown action failed.
+NOTE: VMs managed by the HA stack do not follow the 'start on boot' and
+'boot order' options currently. Those VMs will be skipped by the startup and
+shutdown algorithm as the HA manager itself ensures that VMs get started and
+stopped.
+
Please note that machines without a Start/Shutdown order parameter will always
start after those where the parameter is set, and this parameter only
makes sense between the machines running locally on a host, and not
qm migrate <vmid> <target>
+There are generally two mechanisms for this
+
+* Online Migration (aka Live Migration)
+* Offline Migration
+
+Online Migration
+~~~~~~~~~~~~~~~~
+
When your VM is running and it has no local resources defined (such as disks
on local storage, passed through devices, etc.) you can initiate a live
migration with the -online flag.
+How it works
+^^^^^^^^^^^^
+
+This starts a Qemu Process on the target host with the 'incoming' flag, which
+means that the process starts and waits for the memory data and device states
+from the source Virtual Machine (since all other resources, e.g. disks,
+are shared, the memory content and device state are the only things left
+to transmit).
+
+Once this connection is established, the source begins to send the memory
+content asynchronously to the target. If the memory on the source changes,
+those sections are marked dirty and there will be another pass of sending data.
+This happens until the amount of data to send is so small that it can
+pause the VM on the source, send the remaining data to the target and start
+the VM on the target in under a second.
+
+Requirements
+^^^^^^^^^^^^
+
+For Live Migration to work, there are some things required:
+
+* The VM has no local resources (e.g. passed through devices, local disks, etc.)
+* The hosts are in the same {pve} cluster.
+* The hosts have a working (and reliable) network connection.
+* The target host must have the same or higher versions of the
+ {pve} packages. (It *might* work the other way, but this is never guaranteed)
+
+Offline Migration
+~~~~~~~~~~~~~~~~~
+
If you have local resources, you can still offline migrate your VMs,
as long as all disk are on storages, which are defined on both hosts.
Then the migration will copy the disk over the network to the target host.
the disk images. If you want to change the template, create a linked
clone and modify that.
+Importing Virtual Machines and disk images
+------------------------------------------
+
+A VM export from a foreign hypervisor takes usually the form of one or more disk
+ images, with a configuration file describing the settings of the VM (RAM,
+ number of cores). +
+The disk images can be in the vmdk format, if the disks come from
+VMware or VirtualBox, or qcow2 if the disks come from a KVM hypervisor.
+The most popular configuration format for VM exports is the OVF standard, but in
+practice interoperation is limited because many settings are not implemented in
+the standard itself, and hypervisors export the supplementary information
+in non-standard extensions.
+
+Besides the problem of format, importing disk images from other hypervisors
+may fail if the emulated hardware changes too much from one hypervisor to
+another. Windows VMs are particularly concerned by this, as the OS is very
+picky about any changes of hardware. This problem may be solved by
+installing the MergeIDE.zip utility available from the Internet before exporting
+and choosing a hard disk type of *IDE* before booting the imported Windows VM.
+
+Finally there is the question of paravirtualized drivers, which improve the
+speed of the emulated system and are specific to the hypervisor.
+GNU/Linux and other free Unix OSes have all the necessary drivers installed by
+default and you can switch to the paravirtualized drivers right after importing
+the VM. For Windows VMs, you need to install the Windows paravirtualized
+drivers by yourself.
+
+GNU/Linux and other free Unix can usually be imported without hassle. Note
+that we cannot guarantee a successful import/export of Windows VMs in all
+cases due to the problems above.
+
+Step-by-step example of a Windows OVF import
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Microsoft provides
+https://developer.microsoft.com/en-us/windows/downloads/virtual-machines/[Virtual Machines downloads]
+ to get started with Windows development.We are going to use one of these
+to demonstrate the OVF import feature.
+
+Download the Virtual Machine zip
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+After getting informed about the user agreement, choose the _Windows 10
+Enterprise (Evaluation - Build)_ for the VMware platform, and download the zip.
+
+Extract the disk image from the zip
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Using the `unzip` utility or any archiver of your choice, unpack the zip,
+and copy via ssh/scp the ovf and vmdk files to your {pve} host.
+
+Import the Virtual Machine
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This will create a new virtual machine, using cores, memory and
+VM name as read from the OVF manifest, and import the disks to the +local-lvm+
+ storage. You have to configure the network manually.
+
+ qm importovf 999 WinDev1709Eval.ovf local-lvm
+
+The VM is ready to be started.
+
+Adding an external disk image to a Virtual Machine
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You can also add an existing disk image to a VM, either coming from a
+foreign hypervisor, or one that you created yourself.
+
+Suppose you created a Debian/Ubuntu disk image with the 'vmdebootstrap' tool:
+
+ vmdebootstrap --verbose \
+ --size 10G --serial-console \
+ --grub --no-extlinux \
+ --package openssh-server \
+ --package avahi-daemon \
+ --package qemu-guest-agent \
+ --hostname vm600 --enable-dhcp \
+ --customize=./copy_pub_ssh.sh \
+ --sparse --image vm600.raw
+
+You can now create a new target VM for this image.
+
+ qm create 600 --net0 virtio,bridge=vmbr0 --name vm600 --serial0 socket \
+ --bootdisk scsi0 --scsihw virtio-scsi-pci --ostype l26
+
+Add the disk image as +unused0+ to the VM, using the storage +pvedir+:
+
+ qm importdisk 600 vm600.raw pvedir
+
+Finally attach the unused disk to the SCSI controller of the VM:
+
+ qm set 600 --scsi0 pvedir:600/vm-600-disk-1.raw
+
+The VM is ready to be started.
Managing Virtual Machines with `qm`
------------------------------------
CLI Usage Examples
~~~~~~~~~~~~~~~~~~
-Create a new VM with 4 GB IDE disk.
+Using an iso file uploaded on the 'local' storage, create a VM
+with a 4 GB IDE disk on the 'local-lvm' storage
- qm create 300 -ide0 4 -net0 e1000 -cdrom proxmox-mailgateway_2.1.iso
+ qm create 300 -ide0 local-lvm:4 -net0 e1000 -cdrom local:iso/proxmox-mailgateway_2.1.iso
Start the new VM
projects / pve-docs.git / blobdiff