Wednesday, 17 February 2016

So Who Does Use Linked vCenters?

OK, I am sure that most onboard and I put up my hand, I personally am a fan. When I talk to a lot of clients though, generally I find that most aren't.

Two linked vCenters in Web Client
In the old days we linked the instances together with the linked mode utility (or unlinked it with the same tool). Nice and easy and all of a sudden security and licensing information is shared between vCenter instances. The big gain though was that through the C# client (oh I do miss your usefulness sometimes in this depleting role world) I had a one stop shop to access up to 12 vCenters. Now it is even easier, just have the vCenters in a common Platform Service Controller (PSC) SSO implementation (common site/ multi site doesn't matter).

This in turn enables some very cool features beyond the original benefits. The one that drive me to link mine up was the ability to enable cross vcenter migrations. Being someone that is fortunate to have access to a well equiped lab I have enabled this with VPLEX for the stretched storage and use both SRM 6.1 and vMotion in vCenter to control the migrations (more on that in another blog post I think). 

This blog is not to tell you how to link, that is covered in a lot of other blogs written by very smart people. More I want to draw attention to issues that surface a lot with the newer Enhanced Link Mode with those add-on services that use the web client.

As I have just experienced an issue again I am writing this while it is fresh in the mind. What I see is that with a lot of product teams that do include Web Client plug-ins, there seems to be quite an absence of testing vCenters in Enhanced Linked Mode. Have you ever had this style of conversation:

me)              I am <inset problem description here> in the web client 
developer)   what version are you running
me)              The one listed in requirements
developer)   Are you using the Windows Version of vCenter or the Appliance?
me)              I am using the (whatever) in linked mode
developer)   ohh, we haven't tested that

Anyway some gotchas I seem to experience include:

  • Only one vCenter is supported in the linked set for the plug-in
  • Only the first vCenter is visible to the plug-in
  • Plug-in is unable to differentiate (filter) objects out that are only present within the aligned vCenter (e.g. all datastores across all vCenters are displayed)
So the point of this entry beyond the rant is just to bring attention to the fact that there are some considerations when writing a plug-in for linked vCenters. If you are running into issues and you have got linked vCenters I would suggest that the first step should be test against a stand-alone vCenter. This helps isolate the issue and can help when you are talking to the support/product/vendor teams.

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