You plan to move a distributed on-premises app named App1 to an Azure subscription.
After the planned move, App1 will be hosted on several Azure virtual machines.
You need to ensure that App1 always runs on at least eight virtual machines during planned Azure maintenance.
What should you create?
To ensure that App1 always runs on at least eight virtual machines during planned Azure maintenance, you should create a virtual machine scale set with 10 virtual machine instances. In a virtual machine scale set, the instances are identically configured, and Azure can distribute the load across multiple instances, with a maximum of 20% of the instances being updated at a time during maintenance. This means that at most 2 out of 10 machines will be updated simultaneously, leaving at least 8 machines running, which meets the requirement.
Correct Answer: A VM Scale Set consists of a set of identically configured VMs. Availability Set consists of a set of discrete VMs. No more than 20% of the Scale Set upgrading at any time, then 2 machines out of 10 will have maintenance, the 8 remaining VMs will be up. Virtual machine scale sets are created with five fault domains by default in Azure regions with no zones. For the regions that support zonal deployment of virtual machine scale sets and this option is selected, the default value of the fault domain count is 1 for each of the zones. FD=1 in this case implies that the VM instances belonging to the scale set will be spread across many racks on a best effort basis. Reference: https://docs.microsoft.com/en-us/azure/virtual-machines/manage-availability https://docs.microsoft.com/en-us/learn/modules/build-app-with-scale-sets/2-features-benefits-virtual-machine-scale-sets https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-automatic-upgrade
"Virtual machine scale sets are created with five fault domains by default in Azure regions" I believe you're speaking of update domains?
What part of the question indicates if the VMs are identical or discrete?
Identical because they are to be created to serve App1.
I agree with everyone here saying that answer C will do the job. I wouldn't get hunf up on that. The final line does not say, "which of these choices will meet the requirements". it says, "What SHOULD you create" (emphasis mine). Which of the options is cleanest, most elegant, way forward. Clearly A.
Try making it and you can't. Only 1 update domain can be made if there is 1 fault domain and vice versa.
I think you cannot create an availability set with more then one update and only one fault domain.
Thats true. " While you're upgrading a batch, there could be other concurrent planned or unplanned maintenance activities that could impact the health of your scale set instances. In such cases if more than 20% of the scale set's instances become unhealthy, then the scale set upgrade stops at the end of current batch." https://learn.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-automatic-upgrade#upgrading-vms-in-a-scale-set
Answer is wrong. The correct Answer is A. First: in case you created on fault domain, you are limited with one update domain. You can test this. Second: By default, Azure uses 5 update domains and up to 3 fault domains. So, In case you created 10 vm in scale set. then you will have 2 vm in each update domain. So once one update domain is not available, then you get 4 domains with 8 vms as required.
Well researched and explained. Appreciated! Agree. Very sneaky question leading us to think it is C when ans is A.
this is more like it. thanks
but if A is good, then isn't D better, well costs more
Thank you, now i know why.
on the exam today 6/6/2024
Tested in lab, its not possible to create an Availability Set with only one fault domain and 10 update domains. so C can't be right. I
The Answer here is C Let us first understand the distinction between Scaling and avalability. Scaling: Increase or decrease of VMs depending on loads Availability: Presence of VMs on multiple servers In these 2 definitions Scaling is automatic while availability is manual. In the question, there is a key statement which is "App1 always run on at least 8Vms" this means that App1 must be present on at least 8vms. Here, we don't have any concern with scaling up or scaling down. So, our answer is already tending towards AVAILABILITY SET Now, when you mention Availability set, you are already talking of Domains, both fault and update Now when we have 10 update domains, the app will be distributed into 2VMs per domain and since we have 2VMs per domain, whenever an upgrade is to be done, only 2VMs can go down at a single time making us have 8VM i.e 4 update domains available every time.
Don't panic guys, The Answer is A Reason : When you have 1 fault Domain you can have only 1 Update Domain. (Option C is ruled out)
This was on my exam. The correct answer is provided by the one and only mlantonis.
Correct Answer: C Option A suggests using a virtual machine scale set (VMSS) consisting of 10 virtual machine instances. However, the requirement states that the application must run on at least eight virtual machines during planned Azure maintenance. The virtual machine scale set (VMSS) can automatically scale the number of virtual machine instances based on workload or defined scaling rules. However, it does not guarantee that there will be at least eight virtual machine instances running during planned maintenance. In contrast, option C proposes using an Availability Set with 10 update domains and one fault domain. This ensures that during planned maintenance, at least eight virtual machine instances will be available to run the application, meeting the specified requirement.
Correct Answer: A
There is a lot of confusion around this question. Whilst C can potentially be used in this scenario, the key here is that they specify only one Fault Domain. With one FD you can only create A SINGLE Update Domain, hence the only logical choice is A.
Qustion said "during planned Azure maintenance", AD potentially could be even all down during planned Azure maintenance.
The update domain count must be 1 when fault domain count is 1. ANSWER IS A
A is correct
The minimum number of fault domains required for an availability set containing 10 virtual machines is 31. Each fault domain represents a group of VMs that are placed in separate physical racks or clusters to minimize correlated failures. By distributing the VMs across fault domains, you enhance reliability and reduce the risk of simultaneous failures affecting related VMs. Additionally, an availability set can be configured with up to 20 update domains2. Update domains determine groups of VMs that can be rebooted together during planned maintenance. However, the order of update domains being rebooted may not proceed sequentially.
The minimum number of fault domains required for an availability set containing 10 virtual machines is 3*
A is correct
Answer is A. A-> UD is fixed at 5 for scale set. so during maintenance, 2 Vms will be down at each time. giving us at least 8VMs runing B-> Does not meet the min 8 virtual machines requirement c->Not possible. availability Set will spread out the VM into 2-3 FD depends on region. so min is 2 FD for high availability. ( Look at the comparision between scale sets and availability set under high availability in https://learn.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-orchestration-modes) D->will have min 9 or 10VM running
10 update domains... from 5, we start puting 2 together UD1 - VM1 UD2 - VM2 UD3 - VM3 UD4 - VM4 UD5 - VM5 from here... we start puting the next VMS in the already assigned UD 1 by 1 VM6 -> UD1 VM7 -> UD2 VM8 -> UD3 VM9 -> UD4 VM10 -> UD5 Only 1 Update Domain is updated at time... We will always have 4 update Domain On... which guarantees 8 VMs On always