possible scenarios for availability zones in Azure which work? RRS feed

  • Question

  • Possible scenarios for availability zones in Azure which work?  We are wanting redundancy and HA between the servers if possible. :

    1) A scale set configured with more than one availability zone configured (ie zone 1, zone 2, zone 3)  However when I go to provision SQL there is only one option to choose a availability zone (ie zone 1). I cannot choose two avail zones for SQL.  Noticed I can choose a standard sku LB which allows for redundancy,... can we control which avail zone is migrated to if the datacenter is destroyed?  We want the scale sets and SQL to be in the same avail zone.

    2) Can we configure two IaaS behind a LB (same availability set) with each IaaS configured for a different availability zone?  For example, IaaS A(avail zone 1); IaaS B(avail zone 2); IaaS A and IaaS B are in avail set 3 ?-- is this possible to have a availability set span two different avail zones (1 and 2).

    3) What happens if scale set is configured for default avail zone ( no avail zones chosen)?

    4)  What happens if we use a API instead of LB in option 2 above?

    5) Also we want a entire system (IaaS A w avail set 3; IaaS B w avail set 3; SQL AG w/ 2 replicas,1 internal LB, avail set 4 all to migrate together to the same availability zone.   How would we do this?,... can we configure all IaaS to move to the same regional zone in case the original regional zone is destroyed?  Is it possible to have a LB migrate between availability zones?


    • Edited by kimdav111 Friday, April 12, 2019 10:51 PM
    • Moved by Femisulu-MSFT Saturday, April 13, 2019 2:15 AM better suite here
    Friday, April 12, 2019 10:45 PM

All replies

  • Hi kimdav,

    Load balancer resources are Region specific and not Zone specific. There is no concept of moving or migrating a load balancer from one zone to other.

    When we create a load balancer in a region with 3 availability zones, It will work well till one of the Zone is functioning in that region.

    This link has more information.

    Lets look at your questions now.

    1) Are you planning deploying SQL on VMSS?

    2) Placement groups will help in that case. But i think you can use only one image for all the placement groups.  They are similar to availablity sets only.   You can also specify a parameter called "platformFaultDomainCount" for the whole scale set which manages placing the VM's evenly acros zones. Also check about the Availablity options.

    3) if no zones are chosen, I think it will deploy anywhere. I will check with the internal teams and let you know.

    4) placement groups concepts remain same for API gateway and Load balancer.

    5) With multi zone deployment, Your VM's are already spread across zones. So it will automatically tolerate xone failures. Like we said previously, Moving is not possible and moving is not nercessary. In case of failure in one of the zone and if we setup the auto scaling rules properly, VMSS should spinup machines in healthy zones.

    Let me know if you have more questions.

    Tuesday, April 16, 2019 8:37 AM
  • Any update on this issue?

    If the proposed answer was useful please remember to mark it as the answer so others can easily find it. 

    Friday, April 19, 2019 6:07 PM
  • Any update on this issue? 

    If a suggestion was useful, remember to upvote and mark as answer so others in the community can easily find it. 

    Friday, May 3, 2019 7:08 PM
  • See responses to your questions:

    1) We are planning on deploying VMSS for application / web servers and SQL AGs.   It does not make sense to place SQL in a scale set because the database needs to be synchronized and only a SQL AG allowed this type of AG?

    2) Placement groups would be appropriate because we are not deploy this many servers.   We maybe have 5 sql servers current and roughly 3 web/app servers which need load balancing.  I am thinking creating 5 SQL AG and one scale set for the 3 web/app servers.  During the creation of the scale set we will place the three web/app servers for all all three zones within the region?  Do SQL AGs move within a region?,... I am thinking that SQL AG must stay within a zone.

    However if we changed the design in the previous sentence and placed the 3 web/app servers and its corresponding SQL AG in the same zone how would be provide fail-over to another zone within the region?

    4) I looked at the setup of scale set it let you choose any combination of zones to include not choosing any zones.  I will choose all of the zones just in case.

    5)  We will not be auto-scaling because we are considering at most three web servers.  If we do not auto scale would it not make sense to do a LB?   Is VMSS a feature of scale sets?  


    Tuesday, May 7, 2019 4:19 PM