Managing Images

The Storage system allows HyperCX administrators and users to set up Images, which can be operating systems or data, to be used in Virtual Machines easily. These Images can be used by several Virtual Machines simultaneously, and also shared with other users.

Image Types

The following tyes of images are supported:

  • OS: An bootable disk Image. Every VM template must define one DISK referring to an Image of this type.
  • CDROM: These Images are read-only data. Only one Image of this type can be used in each VM template.
  • DATABLOCK: A datablock Image is a storage for data. These Images can be created from previous existing data, or as an empty drive. Can not be used with LXD containers.

Image Persistency

Image persistency controls how the data is managed inside the image, and how the VM behaves. This is an important concept that should be understood. When creating OS images and DATABLOCKS, or updating any of those types of images, persistency can be specified between two options:

  • Persistent images: When persistent images are used, each image can only be used by a single virtual instance (container or VM). When deploying a workload with persistent image(s), a link is created on the corresponding system datastore, pointing directly to the image in the images datastore. This reduces the deployment time of the VM and, after destroying the VM, the data is kept inside the image. This mode is not recommended for production workloads, only to create golden images that will be used later as non-persistent images.

  • Non-persistent images: When non-persistent images are used, each image can be used many times on different virtual instances. When deploying a workload with non-persistent image(s), the image is fully copied to the corresponding system datastore. This increases the deployment time (PROLOG state) and, after destroying the VM, the data from the virtual instance is fully destroyed. This is the equivalent to any instance deployed in a public cloud and it is the mode that should be used on production workloads.

Bus and mapping driver

Two options under Advanced options should be taken into consideration when creating an image:

Bus

So-called "full virtualization" is a nice feature because it allows you to run any operating system virtualized. However, it's slow because the hypervisor has to emulate actual physical devices such as SCSI/SATA or IDE drives. This emulation is both complicated and inefficient. On most cases, Virtio drivers are recommended. Virtio is a virtualization standard for network and disk device drivers where just the guest's device driver "knows" it is running in a virtual environment, and cooperates with the hypervisor. This enables guests to get high performance network and disk operations, and gives most of the performance benefits of paravirtualization. SCSI/SATA or IDE bus is only recommended for Operating Systems without Virtio drivers. All images provided on Virtalus marketplaces use Virtio as Bus.

Image mapping driver

This options allows to specify the image format. The two most common formats are:

  • raw: Raw disk image format. This format is slightly faster compared to the others since there is no metadata or abstraction layers. Although Raw images provide better performance, only very basic features are available with a Raw image.

  • qcow2: QEMU Copy On Write uses a disk storage optimization strategy that delays allocation of storage until it is actually needed (thin provisioning). This format imposes metadata and an abstraction layer, making it slightly slower than raw format. This is the recommended format to use whenever possible.

Warning

When uploading new images, the mapping driver must be the same that was used when creating the image. If not, the VM or container will fail when being deployed.

Image Life-cycle

Short state State Meaning
lock LOCKED The Image file is being copied or created in the Datastore.
lock LOCKED_USED Image file is being copied or created in the Datastore, with VMs waiting for the operation to finish.
lock LOCKED_USED_PERS Same as LOCKED_USED, for Persistent Images
rdy READY Image ready to be used.
used USED Non-persistent Image used by at least one VM. It can still be used by other VMs.
used USED_PERS Persistent Image is use by a VM. It cannot be used by new VMs.
disa DISABLED Image disabled by the owner, it cannot be used by new VMs.
err ERROR Error state, a FS operation failed. See the Image information with the Administrator for an error message.
dele DELETE The Image is being deleted from the Datastore.
clon CLONE The Image is being cloned.

Managing Images

Users can manage their images using the HyperCX web portal, selecting the Images tab. By default this tab is available in all the views except for the Simple view.

Create Images

OS and CDROM types of Images can be created from an existing file, but for datablock Images you can specify a size and let HyperCX create an empty Image in the Datastore.

If you want to create an OS Image, you need to prepare a contextualized virtual machine, and extract its disk.

Once you have a disk you want to register, you can upload it directly using HyperCX:

Users

You need to choose the Datastore where to register the new Image.

Limitations when Uploading Images from HyperCX

Image file upload to the server via the client browser is possible. The process is as follow:

  • Step 1: The client uploads the whole image file to the server in a temporal file.
  • Step 2: HyperCX registers an Image setting the PATH to that temporal file.
  • Step 3: HyperCX copies the image file to the datastore.
  • Step 4: The temporal file is deleted and the request returns successfully to the user (a message pops up indicating that Image was uploaded correctly).

Note that when file sizes become big (normally over 1GB), and depending on your hardware, it may take long to complete the copying in step 3. Since the upload request needs to stay pending until copying is successful (so it can delete the temp file safely), there might be Ajax timeouts and/or lack of response from the server. This may cause errors, or trigger re-uploads (which re-initiate the loading progress bar).

Clone Images

Existing Images can be cloned to a new one. This is useful to make a backup of an Image before you modify it, or to get a private persistent copy of an Image shared by other user. Note that persistent Images with snapshots cannot be cloned. In order to do so, the user would need to flatten it first, see the snapshots section for more information.

The Images tab contains a dialog for the clone operation: Users

Users

Sharing Images

The users can share their Images with other users in their group, or with all the users in HyperCX. See the Users and Groups documentation for more information.