When working on a design in which there would be two physical datacenters, I started to rethink about why I would create multiple datacenters inside vCenter Server. I noticed that almost all example designs I look at that cover two physical datacenters, also have two datacenters in the vCenter Server design. But why?
When searching for an answer in the vSphere 5.1 documentation, the only reason mentioned to create a datacenter is “You can create multiple datacenters to organize sets of environments.“. But it also states that creating datacenters creates limits: “Inventory objects can interact within a datacenter, but interaction across datacenters is limited. For example, you can hot migrate virtual machines from one host to another host in the same datacenter, but not from a host in one datacenter to a host in a different datacenter.“
For organising objects in vCenter Server, I can also use folders. I can put a datacenter in a folder, I can put a cluster in a folder and I can set permissions at folder level. In other words, creating the logical design in vCenter Server to match the physical design, can also be done using folders, but without the limitations.
My basic statement is: “When I have two physical datacenters, I should not by default create two logical datacenters in vCenter Server”.
Yes, there are reasons to do create two datacenters, but those are very limited. When I asked the question on twitter I got quite a few responses and only one really demanded two logical datacenters, when creating a DMZ and you want to make sure VMs don’t travel between the two datacenters.
Most other cases in which people created two datacenters could also be matched by using folders.
I’m not saying that you shouldn’t be using datacenters, but I just want to see if my statement is correct and that you shouldn’t just blindly create multiple datacenters and thereby limiting functionality like Shared-Nothing Storage VMotion.
Would love to see your comments on that.
Update: Forbes Guthrie wrote a blogpost in response to my question. In his post he shows the do’s and don’ts for the vCenter Server datacenter: Why use the Datacenter object in vCenter?
4 thoughts on “Design question: Why vCenter Server Datacenter?”
In your example I am assuming you have only one vCenter and no SRM etc.
If it is only one vCenter then I personally would still rather have the logical dc’s created to show the physical DC’s to ensure separation of resources, and not allow stretching of clusters across sites. Yes you can do with folders as well as you have shown.
For me most if not all of the multi site physical DC deployments I have designed/deployed have a vCenter per physical DC, and SRM deployed. Given these requirements I have to deploy separate logical datacenters within vCenter.
Personally it is all about who manages the environment and their understanding of the resources deployed. There are many options and considerations to look at here and no right answer
Would you actually do the shared nothing migration across physical DC’s?
Hi G, I started writing a comment which grew to be a post in its own right :)
I think it depends a bit on how connected in terms of network and storage the two physical locations are. As a vSphere admin if everything is contained in one data center, I would expect good connectivity between clusters.
” that you shouldn’t just blindly create multiple datacenters ”
I think the key lies here.
There can be a propensity, especially in VSphere, to utilize tools improperly in the name of organization. Resource Pools can be created ad-naseum and used as folder style containers. This could increase your management time greatly. The same can be said for VApps and Clusters.
Taken in metered doses, and implemented properly, any of these things can work well for their intended purposes, as well as mere organization, with little impact. However, when over-used with too much granularity and specific purpose, any of these items can become cumbersome and ineffective.
My companies environment can be considered similar in the heavy-handed implementation, in the name of control. However, instead of VApps, Folders, or the like, we use single Datacenter, and provide speration with Lan trunks and network segregation. It’s a similar effort, just with a different means.
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