Cloud image consolidation

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By Antonio di Cocco

With IBM SmartCloud Provisioning, users can more easily create and use new virtual machines without having to be concerned about how they are running and where they came from. Users simply pick up, from a catalog, an image to be deployed and run it. This means that to fulfill all requests, the catalog should be as complete as possible. Theoretically it should contain all possible combinations of operating systems plus software, meaning that cloud administrators must manage thousands and thousands of images. As the number of base images increases, management costs quickly increase, which can lead to a much more expensive solution rather than a cost-saver infrastructure. A search on the Internet results in several suggestions to consolidate your image catalog to be as small as possible.

The best way to create and to maintain a small image catalog is to create a few standard configurations depending on the user’s job role. For example, a developer could require an Ubuntu system with IBM Lotus Notes and IBM Rational Software Architect installed on it, but a tester might need a Windows system with Tivoli Endpoint Manager agent, DB2, and various other middleware to run a test scenario. In this case, we can define a standard so that any user can ask for end-usage-driven virtual image deployment. The user will require to deploy an image not selecting it by its content, but based on its job.

Even if the suggestion is good, it might not be easy to implement. In fact, if you are creating your cloud solution “from scratch” you can “force” a user to select, from a small catalog, the best image fitting the user’s requirement. But if you already have had your cloud environment up a running for a while and your image catalog is already out of control, its consolidation might not be an easy job. Cloud administrators should open all virtual images to discover what is in them, understanding their content. And than decide which is the most representative, making them master templates. Just think to do this job for thousands of image.

Luckily, IBM Virtual Image Library can help you in this work.

One of the key features for IBM Virtual Image Library is the capacity to introspect virtual images, understanding their content and allowing cloud administrators to compare between them. In this way, administrators can determine how similar two images are. When you register an operation repository to IBM Virtual Image Library, a discovery process starts. During this phase, information about all images and virtual machines are retrieved from a remote repository.  At this time, only meta data about remote objects are stored locally. Moreover, virtual images are indexed, and their content is read remotely.

After registration is complete, you may start working with your catalog. The most useful operations are:

  • Image comparison: You can select two or more images to compare their content.
  • Image similarity: By selecting an image, you can display list of “similar” images by simply selecting a command.
  • Filter images by their content: You have a powerful search engine to look for images containing specific applications.

As you can imagine, with such a powerful tool, it will be an easier  job to define your master images (defining standard configurations), and consolidate them by merging similar images, reducing them to a smaller and manageable set.

Core function for previous feature is IBM Virtual Image Library capability to introspect remote images. Two types of analyses are available:

  • Basic indexing: Looking to the OS registry for installed software. This analysis is the simplest and quickest that users can run to display image content.
  • Full indexing: Reading an entire image disk and gathering information about all directories and files present in the image.

In both cases, IBM Virtual Image Library will not copy any image locally, but simply connect to remote hypervisor data store to read the image disk, reducing time and network traffic spent during this operation.


IBM Virtual Image Library allows you to introspect remote images to consolidate their number, removing the unnecessary one. After you consolidate them, you can also import the smallest catalog into IBM Virtual Image Library reference repository, allowing you to move across hypervisors. For more information, see the Image portability across hypervisors page in IBM developerWorks.

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