Question

Prism Central Limitations with Image Managment

  • 25 June 2021
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I need some help for understanding Prism Central Image Management. When I read Prism Central Guide (Limitations) I don’t understand “During the copy operation, cluster A becomes unavailable.”

This comment in Prism Central Guide mean that can’t use “cluster A” Prism Element ? Also that mean All acting is suspend like VM Provisioning Operation in "cluster A"?

I want to know side effect and exactly what act is occurred using “cluster A” when becomes unavailable. Please help me.

Thank you for your help :)


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@hoseong I believe you are referring to the following section mentioned in the PC Image Management Limitations guide:

Prism Central can take up to 15 minutes to switch the image propagation from an alternative cluster. For example, if an image is located on clusters A and B. As a result of an image placement policy you applied to that image, cluster A starts copying the image to cluster C. During the copy operation, cluster A becomes unavailable. In such a case, Prism Central takes up to 15 minutes to switch to cluster B and start copying the image from cluster B to cluster C.

 The above section is giving an example for the image placement policy workflow. It is simply stating that let’s suppose if you originally uploaded an image using Prism Central to cluster A and cluster B, so currently only these two clusters (A & B) will have this image available in it. Now, in scenarios where you need to use this image ( originally uploaded on cluster A & B) on a different cluster C, then you can do so using the image placement policy.

In this case, when you try to get this image on cluster C, Prism Central will select any one cluster which originally had the image (for e.g. cluster A) and then will copy it to the cluster C so that cluster C can use this image.

However, in scenarios where when this image is getting copied over to cluster C, cluster A went offline/down due to some issues (for e..g power outage in DC, network issues, etc.) , then Prism Central (PC) will switch the image to copy from cluster B (instead of cluster A since cluster A went down) to cluster C. This switch can take up to 15 minutes to happen - that is what is mentioned in the above example given in the guide. 

This doesn’t mean that when the image is being copied from cluster A to cluster C, cluster A will be down/unavailable. Cluster A stays up/is available for normal use even during when the image is being copied over to cluster C. The above snippet was more of a hypothetical scenario to explain what PC will do in case if cluster A goes down during the image copy operation to cluster C. 
 

I hope that clears that your confusion about the image copy statement mentioned in the guide. Kindly let me know if you have any more questions about this one!

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