In a Nutanix AHV cluster the image service is used to index and manage ISO and virtual disk images for cloning to new VM disks or mounting to the virtual CDROM. With the addition of Prism Central 5.5 or later, this adds a global image service to manage these files across multiple clusters. When managing images from Prism Central we sometimes will see an image show up on a cluster as "inactive". This means the metadata for the image exists but the file does not exist locally on that cluster.

The article "Prism Central: Adding Images to Prism Central" gives a few options to remediate this condition when an image is needed on a certain cluster but is inactive. These methods are useful with Prism Central 5.5 and 5.10 versions.

In Prism Central 5.11 we have added image placement methods to control where your images will be available. During image upload you can choose to select individual clusters where the image should reside, or you can apply a category to the image to utilize an image placement policy. See the section on Image Placement Policies in the Prism Central Guide for official documentation of this feature. 

Image placement policies associate an image category and a cluster category. Images tagged with the chosen category will be placed automatically on any clusters in an associated category. Enforcement of image placement policies can be hard or soft. Hard enforcement disallows placement of an image on any cluster not associated through the policy, while soft enforcement allows manually pushing images to excluded clusters. Both policy types ensure the image will be available on the associated clusters.

For existing images you can manage relocation of images by using policies. For instance when a new cluster is added to Prism Central or an existing image is needed elsewhere you can set up the policy and apply categories for where you want the image, and Prism Central will manage adding or removing the image based on the policy. Making modifications to a soft enforcement policy will add images to selected clusters but will not remove images. Making changes to a hard enforcement policy, or removing clusters from the associated category, will remove policy-managed images from clusters no longer associated with the policy.

For more information on policy based image placement read the Image Placement Policies section in the Prism Web Console Guide.