5 Replies Latest reply on Aug 27, 2019 2:38 PM by TheBobkin

    vSan host question

    CorvetteFan Lurker



      I have a 5 host ESX cluster running ESXi 6.5 update 3.  2 of the hosts were former vSan Nodes and have local storage.  Question is, I'd like to enable them for vSan to make use of the storage.  Can all 5 hosts reside in the same cluster?  I read the following statement from a VMWare Document.


      "A host with no local storage can be added to a vSAN cluster. Note that all hosts in a vSAN cluster require vSAN licensing to use the vSAN datastore regardless of whether they contribute storage to the vSAN datastore."


      I'm only looking to license for vSan the 2 hosts that have the local storage.  If the vSan storage is only aviable on those 2 hosts, I'm fine with that. 



        • 2. Re: vSan host question
          TheBobkin Virtuoso
          VMware EmployeesvExpert

          "It's Possible."

          Alessandro, that is incorrect information and I also have no idea why you posted images and links to completely unrelated information.


          CorvetteFan, this isn't going to be possible in any supported manner for the following reasons:

          1. Yes, adequate vSAN licensing is required for ALL hosts in the a vSAN-enabled cluster regardless of whether they have vSAN-storage configured.

          2. 3 nodes with configured storage is the minimum required unless you wanted to go with something very unorthodox like a 3+2+1/2+3+1 Stretched cluster (requires Enterprise vSAN licensing) with one node with vSAN-storage per site (and then again you would still require a 3rd site for running the Witness) - you also couldn't configure a 2+1 Direct-connect with other compute-only nodes also in the cluster as this requires the vSphere cluster to have precisely 2 members from the start.


          Is there a reason why you don't just put these hosts in their own 2+1 or 1+1+1 cluster and maybe run the Witness on one of the remaining nodes (in their own non-vSAN cluster)?



          • 3. Re: vSan host question
            CorvetteFan Lurker

            Thank you for the reply.  The reason is compute.  Resources are very tight here.  Having 2 clusters will not allow for enough capacity for a host failure and the shared storage is at its limit.  New hardware is on the way, but it this is an immediate need. 

            • 4. Re: vSan host question
              AlessandroRomeo68 Master

              HI TheBobki.


              I probably misunderstood the question.

              Writes "Can all 5 hosts reside in the same cluster?" but then specifies that all the licenses are needed, I considered it as an answer.

              Then he writes "I'm only looking to license for vSan the 2 hosts that have the local storage"... and my answer refers to the latter.

              There are no problems for two who are licensed.



              Alessandro Romeo

              • 5. Re: vSan host question
                TheBobkin Virtuoso
                vExpertVMware Employees

                I can't say for 6.5 U3 as I don't have a cluster configured with this on hand (from home) but in 6.7 (GA) there actually isn't a guard-rail preventing from adding additional nodes to a 2-node cluster e.g. it will prevent from initially configuring it if more than 2 nodes in the cluster but it doesn't prevent adding nodes after (and IMO it should, so I will be following up on this) - this isn't a supported configuration so all onus is on you if anything goes wrong, but in theory you could configure a 2+1 cluster (DO NOT run the Witness VM on the cluster), and add the other nodes as compute-only after (or just a supported Stretched-cluster configuration but this requires Enterprise licensing). You would still require vSAN licenses for the compute-only nodes but if this is a temporary arrangement and you have valid Evaluation licenses this would suffice.


                While I understand what "immediate need" can mean, I wouldn't advise janking together a cluster on the fly to meet these needs - there are almost always other approaches that can be taken e.g. validating that 100% of what is running/stored on the cluster(s) is actually required/not bloated/not running on snapshots/not over-provisioned (storage and compute) etc. - unless you know your environment extremely intimately you would be shocked at how much bloat there can potentially be.