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Manual Chapter: Managing vCMP Virtual Disks
Manual Chapter
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Overview: Managing vCMP virtual disks

A virtual disk is the portion of disk space that the system has allocated to a guest. Each virtual disk is implemented as an image file with an .img extension, such as guest_A.img.

You do not explicitly create virtual disks. The vCMP system automatically creates a virtual disk when you set a guest to the Provisioned or Deployed state. However, after you have created and deployed all guests, a host or guest administrator can delete virtual disks on the system as a way to optimize disk space.

Using the BIG-IP Configuration utility or the Traffic Management Shell (tmsh), you can delete virtual disks on the system as a way to optimize disk space.

About virtual disk allocation

For each vCMP guest, the host automatically creates a sparse file to be used as a virtual disk. This amount of disk space can grow to 100 GB, and is not dependent on the number of cores that you configure for that guest. For example, allocating two cores to guest_A provides the same amount of available disk space for the guest as allocating four cores to the guest.

Note that you cannot explicitly create virtual disks; instead, the BIG-IP system creates virtual disks when the guest changes to a Provisioned or Deployed state. You can create a guest that remains in the Configured state, but in this case, the guest has no virtual disk allocated to it.

About virtual disk images

A virtual disk is in the form of an image that resides in the /shared/vmdisks directory. The default file name that the BIG-IP system initially assigns to a virtual disk is the guest name plus a .img extension (for example, guestA.img). Using the BIG-IP Configuration utility or the Traffic Management Shell (ttmsh), you identify and manage virtual disks on the system using these file names.

About virtual disk templates

If you need to create multiple guests, you most likely want to minimize the time that the vCMP system needs to create all of the virtual disks. The vCMP system automatically accomplishes this through a feature known as virtual disk templates. A virtual disk template is a virtual disk image that contains a fresh installation of an initial ISO image. Its purpose is to minimize the time that the system uses to create virtual disks on the system.

When you provision a guest on the system, with a specific version of BIG-IP software installed, the system automatically creates a virtual disk template pertaining to that ISO image. Later, when you create other guests that use the same ISO image, the system instantiates a copy of the virtual disk template to more rapidly create the virtual disks for those guests. The vCMP system creates a separate virtual disk template for each initial image that you initially configure for a guest.

No user intervention is required to use this feature. On the vCMP system, you can view a list of the system-created templates, or you can delete a template, but you cannot explicitly create or modify a template.

Important: By default, the virtual disk template feature is enabled on hardware platforms with solid state drives and disabled on platforms with spinning hard drives. If you want to use virtual disk templates on platforms with spinning drives, you must explicitly enable the feature, using the db variable vcmp.installer.use_vdisk_templates .

Viewing the list of virtual disk templates

Before performing this task, confirm that you have created and provisioned at least one vCMP guest after upgrading the host to the latest version.
You perform this task when you want to view the virtual disk templates that the vCMP system has created.
Note: The virtual disk template list shows a separate virtual disk template for each initial image that you initially configured for a guest.
  1. On the Main tab, click vCMP > Template List.
  2. View all information displayed. For example, the following shows a sample list of virtual disk templates on the vCMP host.
     List of virtual disk templates
After performing this task, you can see the virtual disk templates that the vCMP system can use when installing the initial image.

Deleting virtual disk templates

You perform this task when you want to delete a virtual disk template on the vCMP host. On the host, there is a separate virtual disk template corresponding to each initial image that you previously installed on a guest. The reason for deleting virtual disk templates is to conserve disk space. You should delete any virtual disk templates that the host will no longer use when creating vCMP guests.
  1. On the Main tab, click vCMP > Template List.
  2. In the Name column, locate the name of the virtual disk template that you want to delete.
  3. To the left of the virtual disk template name, select the check box.
  4. Click Delete. The system prompts you to confirm the delete action.
  5. Click Delete.
After performing this task, the deleted virtual disk template is no longer available for the vCMP system to use. Note, however, that the system can recreate the template if another guest is provisioned using that same software version.

Enabling and disabling the virtual disk template feature

You can perform this task to enable or disable the virtual templates feature on any vCMP-enabled system. The virtual templates feature is useful for minimizing the time that the system uses to create virtual disks on the system. By default, the feature is enabled on platforms with solid-state drives. On platforms with spinning drives, the virtual disk templates feature is automatically disabled due to potential stress and latency on spinning drives during guest provisioning. For this reason, F5 Networks recommends that for platforms with spinning drives, you enable virtual disk templates in a test environment only, whenever you need to create multiple guests running the same BIG-IP software version.

  1. Log in to the BIG-IP system and access tmsh.
  2. At the tmsh command prompt, type modify sys db vcmp.installer.use_vdisk_templates value default|enabled|disabled
    Value Description
    default When set to default, the db variable vcmp.installer.use_vdisk_templates enables the virtual disk templates feature on any vCMP-enabled platforms with solid-state drives and disables virtual disk templates on any vCMP-enabled platforms with spinning drives. The default value is default.
    enabled When set to enabled, the db variable vcmp.installer.use_vdisk_templates enables the virtual disk templates feature on all vCMP-enabled hardware platforms, regardless of drive type.
    disabled When set to disabled, the db variable vcmp.installer.use_vdisk_templates disables the virtual disk templates feature on all vCMP-enabled hardware platforms, regardless of drive type.

Viewing the virtual disk templates db variable

You can perform this task to view the current value of the db variable vcmp.installer.use_vdisk_templates.

  1. Log in to the BIG-IP system and access tmsh.
  2. At the tmsh command prompt, type list sys db vcmp.installer.use_vdisk_templates The BIG-IP system displays the current value of the db variable vcmp.installer.use_vdisk_templates.

About virtual disk detachment and re-attachment

When a vCMP guest has no virtual disk and moves from the Configured state to the Provisioned state, the system creates a virtual disk and attaches the disk to the guest. This attachment ensures that only that guest can use the virtual disk. A guest can have only one virtual disk attached to it at any one time.

A virtual disk can become unattached from a guest when you perform one of these actions:

  • Delete a guest.
  • Change the Virtual Disk property of the guest to None. Note that to perform this action, you must first change the guest state to Configured.

With either of these actions, the system retains the virtual disks on the system for future use.

You can attach an existing, unattached virtual disk to a new guest that you create. Attaching an existing virtual disk to a newly-created guest saves the BIG-IP system from having to create a new virtual disk for the guest.

Detaching virtual disks from a vCMP guest

Before you can detach a virtual disk from a guest, you must be logged into the vCMP host. Also, you must change the Requested State property on the guest to Configured.
You can detach a virtual disk from the guest, but retain the virtual disk on the BIG-IP system so that you can attach it to another guest later.
Important: Unattached virtual disks consume disk space on the system. To prevent unattached virtual disks from depleting available disk space, routinely monitor the number of unattached virtual disks that exist on the system.
  1. On the Main tab, click vCMP > Guest List. This displays a list of guests on the system.
  2. In the Name column, locate the relevant guest name, and to the left of the name, select the check box.
  3. Click the Configured button.
  4. In the Name column, click the guest name.
  5. From the Virtual Disk list, select the default value, None.
  6. Click Update.
The vCMP guest no longer has any virtual disk attached to it.

Viewing virtual disks not attached to a vCMP guest

Before you can view unattached virtual disks, you must be logged into the vCMP host.
You can view virtual disks that are not attached to a vCMP guest so that you can monitor virtual disks that might be unused but still consuming disk space.
  1. On the Main tab, click vCMP > Virtual Disk List.
  2. Locate the Virtual Disk List area of the screen.
  3. To the right of the list of virtual disk names, note any disks that do not have any guest names associated with them. These disks are unattached.

Attaching a detached virtual disk to a vCMP guest

Before you begin this task, ensure that:

  • You are logged into the vCMP host.
  • The guest to which you are attaching the virtual disk is in the Configured state.
  • The virtual disk is not currently be attached to another guest.

It is possible for a virtual disk to become detached from a vCMP guest. A disk that is no longer attached to a guest is known as an unattached virtual disk.

You can attach an unattached virtual disk to another guest either when you create the guest or when you modify the Virtual Disk property of a guest.

  1. On the Main tab, click vCMP > Guest List. This displays a list of guests on the system.
  2. In the Name column, click the name of the guest that you want to view.
  3. From the Properties list, select Advanced.
  4. From the Virtual Disk list, select a file name. The guest uses the newly-selected virtual disk when being deployed.
  5. Click Update.

Deleting a virtual disk from the BIG-IP system

Before deleting a virtual disk, ensure that you are logged into the vCMP host.

Using the BIG-IP Configuration utility, you can delete a virtual disk from the system.

Important: This is the only way to delete a virtual disk from the system. If you delete the associated guest instead, the system retains the virtual disk for re-use by another guest later.
  1. On the Main tab, click vCMP > Virtual Disk List.
  2. Locate the Virtual Disk List area of the screen.
  3. In the Name column, locate the name of the virtual disk that you want to delete.
  4. To the left of the virtual disk name, select the check box.
  5. Click Delete. The system prompts you to confirm the delete action.
  6. Click Delete.
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