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10.2. Virtual Machine Pool Tasks

10.2.1. Creating a Virtual Machine Pool

You can create a virtual machine pool that contains multiple virtual machines that have been created based on a common template.

Procedure 10.1. Creating a Virtual Machine Pool

  1. Click the Pools tab.
  2. Click the New button to open the New Pool window.
  3. Use the drop down-list to select the Cluster or use the selected default.
  4. Use the Template drop-down menu to select the required template and version or use the selected default. A template provides standard settings for all the virtual machines in the pool.
  5. Use the Operating System drop-down list to select an Operating System or use the default provided by the template.
  6. Use the Optimized for drop-down list to optimize virtual machines for either Desktop use or Server use.
  7. Enter a Name and Description, any Comments, and the Number of VMs for the pool.
  8. Enter the number of virtual machines to be prestarted in the Prestarted VMs field.
  9. Select the Maximum number of VMs per user that a single user is allowed to run in a session. The minimum is one.
  10. Select the Delete Protection check box to enable delete protection.
  11. Optionally, click the Show Advanced Options button and perform the following steps:
    1. Click the Type tab:
      1. Select a Pool Type:
        • Manual - The administrator is responsible for explicitly returning the virtual machine to the pool.
        • Automatic - The virtual machine is automatically returned to the virtual machine pool.
      2. Select the Stateful Pool check box to ensure that virtual machines are started in a stateful mode. This means that changes made by a previous user will persist on a virtual machine.
    2. Click the Console tab:
      1. Select the Override SPICE Proxy check box.
      2. In the Overridden SPICE proxy address text field, specify the address of a SPICE proxy to override the global SPICE proxy.
  12. Click OK.
You have created and configured a virtual machine pool with the specified number of identical virtual machines. You can view these virtual machines in the Virtual Machines resource tab, or in the details pane of the Pools resource tab; a virtual machine in a pool is distinguished from independent virtual machines by its icon.

10.2.2. Explanation of Settings and Controls in the New Pool and Edit Pool Windows

10.2.2.1. New Pool and Edit Pool General Settings Explained

The following table details the information required on the General tab of the New Pool and Edit Pool windows that are specific to virtual machine pools. All other settings are identical to those in the New Virtual Machine window.
Table 10.1. General settings
Field Name
Description
Template
The template and template sub version on which the virtual machine pool is based. If you create a pool based on the latest sub version of a template, all virtual machines in the pool, when rebooted, will automatically receive the latest template version. For more information on configuring templates for virtual machines see Virtual Machine General Settings Explained and Explanation of Settings in the New Template and Edit Template Windows in the Virtual Machine Management Guide.
Description
A meaningful description of the virtual machine pool.
Comment
A field for adding plain text human-readable comments regarding the virtual machine pool.
Prestarted VMs
Allows you to specify the number of virtual machines in the virtual machine pool that will be started before they are taken and kept in that state to be taken by users. The value of this field must be between 0 and the total number of virtual machines in the virtual machine pool.
Number of VMs/Increase number of VMs in pool by
Allows you to specify the number of virtual machines to be created and made available in the virtual machine pool. In the edit window it allows you to increase the number of virtual machines in the virtual machine pool by the specified number. By default, the maximum number of virtual machines you can create in a pool is 1000. This value can be configured using the MaxVmsInPool key of the engine-config command.
Maximum number of VMs per user
Allows you to specify the maximum number of virtual machines a single user can take from the virtual machine pool at any one time. The value of this field must be between 1 and 32,767.
Delete Protection
Allows you to prevent the virtual machines in the pool from being deleted.

10.2.2.2. New and Edit Pool Type Settings Explained

The following table details the information required on the Type tab of the New Pool and Edit Pool windows.
Table 10.2. Type settings
Field Name
Description
Pool Type
This drop-down menu allows you to specify the type of the virtual machine pool. The following options are available:
  • Automatic: After a user finishes using a virtual machine taken from a virtual machine pool, that virtual machine is automatically returned to the virtual machine pool.
  • Manual: After a user finishes using a virtual machine taken from a virtual machine pool, that virtual machine is only returned to the virtual machine pool when an administrator manually returns the virtual machine.
Stateful Pool
Specify whether the state of virtual machines in the pool is preserved when a virtual machine is passed to a different user. This means that changes made by a previous user will persist on the virtual machine.

10.2.2.3. New Pool and Edit Pool Console Settings Explained

The following table details the information required on the Console tab of the New Pool or Edit Pool window that is specific to virtual machine pools. All other settings are identical to those in the New Virtual Machine and Edit Virtual Machine windows.
Table 10.3. Console settings
Field Name
Description
Override SPICE proxy
Select this check box to enable overriding the SPICE proxy defined in global configuration. This feature is useful in a case where the user (who is, for example, connecting via the User Portal) is outside of the network where the hosts reside.
Overridden SPICE proxy address
The proxy by which the SPICE client will connect to virtual machines. This proxy overrides both the global SPICE proxy defined for the Red Hat Virtualization environment and the SPICE proxy defined for the cluster to which the virtual machine pool belongs, if any. The address must be in the following format: 
protocol://[host]:[port]

10.2.2.4. Virtual Machine Pool Host Settings Explained

The following table details the options available on the Host tab of the New Pool and Edit Pool windows.
Table 10.4. Virtual Machine Pool: Host Settings
Field Name
Sub-element
Description
Start Running On
 
Defines the preferred host on which the virtual machine is to run. Select either:
  • Any Host in Cluster - The virtual machine can start and run on any available host in the cluster.
  • Specific Host(s) - The virtual machine will start running on a particular host in the cluster. However, the Manager or an administrator can migrate the virtual machine to a different host in the cluster depending on the migration and high-availability settings of the virtual machine. Select the specific host or group of hosts from the list of available hosts.
Migration Options
Migration mode
Defines options to run and migrate the virtual machine. If the options here are not used, the virtual machine will run or migrate according to its cluster's policy.
  • Allow manual and automatic migration - The virtual machine can be automatically migrated from one host to another in accordance with the status of the environment, or manually by an administrator.
  • Allow manual migration only - The virtual machine can only be migrated from one host to another manually by an administrator.
  • Do not allow migration - The virtual machine cannot be migrated, either automatically or manually.
 
Use custom migration policy
Defines the migration convergence policy. If the check box is left unselected, the host determines the policy.
  • Legacy - Legacy behavior of 3.6 version. Overrides in vdsm.conf are still applied. The guest agent hook mechanism is disabled.
  • Minimal downtime - Allows the virtual machine to migrate in typical situations. Virtual machines should not experience any significant downtime. The migration will be aborted if virtual machine migration does not converging after a long time (dependent on QEMU iterations, with a maximum of 500 milliseconds). The guest agent hook mechanism is enabled.
  • Suspend workload if needed - Allows the virtual machine to migrate in most situations, including when the virtual machine is running a heavy workload. Virtual machines may experience a more significant downtime. The migration may still be aborted for extreme workloads. The guest agent hook mechanism is enabled.
 
Use custom migration downtime
This check box allows you to specify the maximum number of milliseconds the virtual machine can be down during live migration. Configure different maximum downtimes for each virtual machine according to its workload and SLA requirements. Enter 0 to use the VDSM default value.
 
Auto Converge migrations
Only activated with Legacy migration policy. Allows you to set whether auto-convergence is used during live migration of the virtual machine. Large virtual machines with high workloads can dirty memory more quickly than the transfer rate achieved during live migration, and prevent the migration from converging. Auto-convergence capabilities in QEMU allow you to force convergence of virtual machine migrations. QEMU automatically detects a lack of convergence and triggers a throttle-down of the vCPUs on the virtual machine. Auto-convergence is disabled globally by default.
  • Select Inherit from cluster setting to use the auto-convergence setting that is set at the cluster level. This option is selected by default.
  • Select Auto Converge to override the cluster setting or global setting and allow auto-convergence for the virtual machine.
  • Select Don't Auto Converge to override the cluster setting or global setting and prevent auto-convergence for the virtual machine.
 
Enable migration compression
Only activated with Legacy migration policy. The option allows you to set whether migration compression is used during live migration of the virtual machine. This feature uses Xor Binary Zero Run-Length-Encoding to reduce virtual machine downtime and total live migration time for virtual machines running memory write-intensive workloads or for any application with a sparse memory update pattern. Migration compression is disabled globally by default.
  • Select Inherit from cluster setting to use the compression setting that is set at the cluster level. This option is selected by default.
  • Select Compress to override the cluster setting or global setting and allow compression for the virtual machine.
  • Select Don't compress to override the cluster setting or global setting and prevent compression for the virtual machine.
 
Pass-Through Host CPU
This check box allows virtual machines to take advantage of the features of the physical CPU of the host on which they are situated. This option can only be enabled when Do not allow migration is selected.
Configure NUMA
NUMA Node Count
The number of virtual NUMA nodes to assign to the virtual machine. If the Tune Mode is Preferred, this value must be set to 1.
 
Tune Mode
The method used to allocate memory.
  • Strict: Memory allocation will fail if the memory cannot be allocated on the target node.
  • Preferred: Memory is allocated from a single preferred node. If sufficient memory is not available, memory can be allocated from other nodes.
  • Interleave: Memory is allocated across nodes in a round-robin algorithm.
 
NUMA Pinning
Opens the NUMA Topology window. This window shows the host's total CPUs, memory, and NUMA nodes, and the virtual machine's virtual NUMA nodes. Pin virtual NUMA nodes to host NUMA nodes by clicking and dragging each vNUMA from the box on the right to a NUMA node on the left.

10.2.2.5. New Pool and Edit Pool Resource Allocation Settings Explained

The following table details the information required on the Resource Allocation tab of the New Pool and Edit Pool windows that are specific to virtual machine pools. All other settings are identical to those in the New Virtual Machine window. See Virtual Machine Resource Allocation Settings Explained in the Virtual Machine Management Guide for more information.
Table 10.5. Resource Allocation settings
Field Name
Sub-element
Description
Disk Allocation
Auto select target
Select this check box to automatically select the storage domain that has the most free space. The Target and Profile fields are disabled.
Format
This field is read-only and always displays QCOW2 unless the storage domain type is OpenStack Volume (Cinder), in which case the format is Raw.

10.2.3. Editing a Virtual Machine Pool

10.2.3.1. Editing a Virtual Machine Pool

After a virtual machine pool has been created, its properties can be edited. The properties available when editing a virtual machine pool are identical to those available when creating a new virtual machine pool except that the Number of VMs property is replaced by Increase number of VMs in pool by.

Note

When editing a virtual machine pool, the changes introduced affect only new virtual machines. Virtual machines that existed already at the time of the introduced changes remain unaffected.

Procedure 10.2. Editing a Virtual Machine Pool

  1. Click the Pools resource tab, and select a virtual machine pool from the results list.
  2. Click Edit to open the Edit Pool window.
  3. Edit the properties of the virtual machine pool.
  4. Click Ok.

10.2.3.2. Prestarting Virtual Machines in a Pool

The virtual machines in a virtual machine pool are powered down by default. When a user requests a virtual machine from a pool, a machine is powered up and assigned to the user. In contrast, a prestarted virtual machine is already running and waiting to be assigned to a user, decreasing the amount of time a user has to wait before being able to access a machine. When a prestarted virtual machine is shut down it is returned to the pool and restored to its original state. The maximum number of prestarted virtual machines is the number of virtual machines in the pool.
Prestarted virtual machines are suitable for environments in which users require immediate access to virtual machines which are not specifically assigned to them. Only automatic pools can have prestarted virtual machines.

Procedure 10.3. Prestarting Virtual Machines in a Pool

  1. Use the Pools resource tab, tree mode, or the search function to find and select the virtual machine pool in the results list.
  2. Click Edit to open the Edit Pool window.
  3. Enter the number of virtual machines to be prestarted in the Prestarted VMs field.
  4. Select the Pool tab. Ensure Pool Type is set to Automatic.
  5. Click OK.
You have set a number of prestarted virtual machines in a pool. The prestarted machines are running and available for use.

10.2.3.3. Adding Virtual Machines to a Virtual Machine Pool

If you require more virtual machines than originally provisioned in a virtual machine pool, add more machines to the pool.

Procedure 10.4. Adding Virtual Machines to a Virtual Machine Pool

  1. Use the Pools resource tab, tree mode, or the search function to find and select the virtual machine pool in the results list.
  2. Click Edit to open the Edit Pool window.
  3. Enter the number of additional virtual machines to add in the Increase number of VMs in pool by field.
  4. Click OK.
You have added more virtual machines to the virtual machine pool.

10.2.3.4. Detaching Virtual Machines from a Virtual Machine Pool

You can detach virtual machines from a virtual machine pool. Detaching a virtual machine removes it from the pool to become an independent virtual machine.

Procedure 10.5. Detaching Virtual Machines from a Virtual Machine Pool

  1. Use the Pools resource tab, tree mode, or the search function to find and select the virtual machine pool in the results list.
  2. Ensure the virtual machine has a status of Down because you cannot detach a running virtual machine.
    Click the Virtual Machines tab in the details pane to list the virtual machines in the pool.
  3. Select one or more virtual machines and click Detach to open the Detach Virtual Machine(s) confirmation window.
  4. Click OK to detach the virtual machine from the pool.

Note

The virtual machine still exists in the environment and can be viewed and accessed from the Virtual Machines resource tab. Note that the icon changes to denote that the detached virtual machine is an independent virtual machine.
You have detached a virtual machine from the virtual machine pool.

10.2.4. Removing a Virtual Machine Pool

You can remove a virtual machine pool from a data center. You must first either delete or detach all of the virtual machines in the pool. Detaching virtual machines from the pool will preserve them as independent virtual machines.

Procedure 10.6. Removing a Virtual Machine Pool

  1. Use the Pools resource tab, tree mode, or the search function to find and select the virtual machine pool in the results list.
  2. Click Remove to open the Remove Pool(s) confirmation window.
  3. Click OK to remove the pool.
You have removed the pool from the data center.
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