Azure VM 99.99% SLA with Minimal Zones

AZ-900 By islever Editorial Last updated

Describe the core architectural components of Azure

Short answer

B The solution fails because 99.99% SLA requires VMs to be distributed across two or more Availability Zones, whereas the proposed strategy uses only one zone.

Question

Note: The question is included in a number of questions that depicts the identical set-up. However, every question has a distinctive result. Establish if
the solution satisfies the requirements.
You are tasked with deploying a critical LOB application, which will be installed on a virtual machine, to Azure.
You are informed that the application deployment strategy should allow for a guaranteed availability of 99.99 percent. You need to make sure that the strategy
requires as little virtual machines and availability zones as possible.
Solution: You include two virtual machines and one availability zone in your strategy.
Does the solution meet the goal?
  1. Yes
  2. No Correct Answer

Key Takeaways

The question tests the specific SLA tiers for Azure VMs; the trap is assuming that multiple VMs in a single zone suffice for 99.99%, when cross-zone redundancy is mandatory.

Achieving a 99.99% availability SLA for Azure Virtual Machines requires deploying instances across two or more Availability Zones, not just one.

Common mistake: Learners often select 'Yes' because they believe having two VMs provides sufficient redundancy, failing to realize that both being in the same zone creates a single point of failure for that zone's infrastructure.

Expert Analysis

Why the Answer Is Correct

The solution does not meet the goal, making B the correct choice. According to Microsoft's official Service Level Agreements (SLAs), a 99.99% uptime guarantee for Azure Virtual Machines is only available when you deploy two or more VM instances across two or more Availability Zones within the same region. Deploying two VMs in a single Availability Zone results in an SLA of 99.95%, which falls short of the required 99.99%. Therefore, the strategy must include at least two distinct zones to eliminate the single point of failure associated with a zone outage.

Why the Other Options Are Wrong

Option A ('Yes') is incorrect because it validates a configuration that only guarantees 99.95% availability. The requirement explicitly states a need for 99.99% guaranteed availability, which is a higher tier reserved for multi-zone deployments. Even though the solution minimizes resources by using only two VMs, it fails the primary constraint of high availability if those VMs are confined to one zone.

Community Comment Notes

Community consensus strongly supports answer B. As noted by user BinuRaj and others, the official documentation specifies that 99.99% connectivity is guaranteed only for VMs deployed across two or more Availability Zones. Users like AntonioTech and Meesquared emphasize that a single Availability Zone acts as a single point of failure, meaning any maintenance or outage in that zone affects all VMs within it, preventing the achievement of the 99.99% target.

Official Reference

https://azure.microsoft.com/en-us/support/legal/sla/virtual-machines/

This link opens the official vendor documentation in a new tab.

Exam Strategy

Always memorize the exact SLA percentages for core Azure services. For VMs, remember: Single Instance = 99.9%, Two Instances in Same Region (Availability Set) = 99.95%, Two+ Instances Across Two+ Availability Zones = 99.99%. Exam questions often test these specific thresholds.

Frequently Asked Questions

Why isn't 99.95% acceptable if I use two VMs?

The question explicitly demands a guaranteed availability of 99.99%. While 99.95% is good, it does not meet the strict business requirement stated in the scenario.

Does adding a Load Balancer improve the SLA?

No. The SLA depends on the underlying infrastructure resilience. Without distributing VMs across multiple Availability Zones, a Load Balancer cannot protect against a full zone outage.

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Discussion 19 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 19

  1. BinuRaj 👍 130
    SLA for Virtual Machines Last updated: July 2020 For all Virtual Machines that have two or more instances deployed across two or more Availability Zones in the same Azure region, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.99% of the time. For all Virtual Machines that have two or more instances deployed in the same Availability Set or in the same Dedicated Host Group, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.95% of the time. For any Single Instance Virtual Machine using Premium SSD or Ultra Disk for all Operating System Disks and Data Disks, we guarantee you will have Virtual Machine Connectivity of at least 99.9%. For any Single Instance Virtual Machine using Standard SSD Managed Disks for Operating System Disk and Data Disks, we guarantee you will have Virtual Machine Connectivity of at least 99.5%. For any Single Instance Virtual Machine using Standard HDD Managed Disks for Operating System Disks and Data Disks, we guarantee you will have Virtual Machine Connectivity of at least 95%. Answer correct.
  2. iwarakorn 👍 45
    Answer is NO For all Virtual Machines that have two or more instances deployed across two or more Availability Zones in the same Azure region, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.99% of the time. For all Virtual Machines that have two or more instances deployed in the same Availability Set or in the same Dedicated Host Group, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.95% of the time.
  3. BeauChateau 👍 11 Answered B
    B. No. The solution does not meet the goal. Having only two virtual machines and one availability zone cannot guarantee 99.99% availability, as it only offers 99.95% SLA. To achieve a guaranteed 99.99% availability, the strategy should include at least two or more virtual machines in two or more availability zones.
  4. AntonioTech 👍 7
    The answer is B. No The solution does not meet the goal. Azure's SLA for Virtual Machines with a single instance is 99.5% availability. To achieve a guaranteed availability of 99.99%, you would need to deploy the application in an architecture that takes advantage of Azure's higher availability options, such as Availability Zones. For an SLA of 99.99%, deploying the application in at least two Availability Zones would be recommended. This would ensure that your application is highly available across separate physical locations, each with its own power, cooling, and networking, reducing the risk of a single point of failure. Simply deploying two virtual machines in a single Availability Zone would not achieve the desired level of availability.
  5. Meesquared 👍 5 Answered B
    A single availability zone still creates a single point of failure. For 99.99% availability, Microsoft requires at least two VMs deployed across two or more availability zones in the same region. Correct Strategy: ✅ Deploy two or more VMs in two availability zones using an availability set or zone redundancy. This ensures high availability even if one zone goes down.
Show 14 more comments
  1. lakspri 👍 4
    B. No Availability Zones in Azure provide high availability by distributing resources across physically separate locations within an Azure region. To achieve a guaranteed availability of 99.99%, you typically need to leverage more than one Availability Zone. Including just one Availability Zone does not provide the redundancy required to ensure 99.99% availability, as a single Availability Zone can still be a single point of failure. A more appropriate strategy would be to use two virtual machines spread across two different Availability Zones. This way, if one Availability Zone goes down, the other can still ensure the availability of the application, thus meeting the 99.99% availability requirement. So, including two virtual machines but only one availability zone does not meet the goal.
  2. Payu1994 👍 2
    The proposed solution does not meet the goal of achieving a guaranteed availability of 99.99 percent. Let me explain why: Virtual Machines (VMs): Including two virtual machines is a good step for redundancy and fault tolerance. However, it’s not sufficient on its own to achieve the desired availability. VMs can still experience downtime due to maintenance, failures, or other issues. Availability Zones: The inclusion of one availability zone is a positive move, but it’s not enough to meet the stringent availability requirement. Availability zones provide isolation from data center failures within a region, but for 99.99 percent availability, we need more redundancy.
  3. suresh_fx 👍 2
    No, the solution does not meet the goal. In order to achieve a guaranteed availability of 99.99%, a higher level of redundancy and fault tolerance is required. The solution should include deploying the virtual machines across multiple availability zones or regions to provide geographic redundancy and fault tolerance. Additionally, the virtual machines should be configured with load balancing to ensure high availability and to distribute traffic evenly across the instances.
  4. blobstorage 👍 2
    For all Virtual Machines that have two or more instances deployed across two or more Availability Zones in the same Azure region, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.99% of the time.
  5. AlefZERO 👍 2 Answered B
    Avaiability zones are meant to provide resilience - devices from different availability zones are physically seperate over large distnaces - this ensures security. Having only one availability zone provides no resilience at all.
  6. Kanders 👍 2
    B. No - You would need to include a minimum of two VMs and two availability zones to reach 99.99%
  7. Molota 👍 2 Answered B
    You need at least 2 virtual machines and 2 availability zone
  8. tg_04 👍 1 Answered B
    No, the solution does not meet the goal of guaranteeing an availability of 99.99 percent. In Azure, achieving a Service Level Agreement (SLA) of 99.99 percent availability for virtual machines typically requires deploying them across at least two availability zones. This is because availability zones are designed to provide high availability by isolating resources in separate physical locations within a region, protecting against zone-level failures. If you only include one availability zone, the virtual machines would be susceptible to outages that affect that zone, thereby compromising the availability guarantee. To meet the 99.99 percent availability requirement, you should deploy at least two virtual machines across two different availability zones. This configuration ensures that if one zone experiences an issue, the other zone can continue to operate, thus maintaining the required level of availability for the critical line-of-business application.
  9. ElPitu97 👍 1 Answered B
    b-no are physically separated zones within an Azure region. Availability zones guarantee virtual machine connectivity to at least one instance at least 99.99% of the time when you have two or more instances deployed across two or more Availability Zones in the same Azure region. Overview of virtual machines in Azure - Azure Virtual Machines | Microsoft Learn
  10. Bazking 👍 1
    This question is confusing if you don't fully understand an availability zone as in other questions it might say availability zoneS with an S at the end it changes everything. The best way I remember it is everytime it says availability zone think of it as data center. So if it said 2 availability zones or availability zoneS then you know its 2 data centers.
  11. AlekksMaciel 👍 1 Answered B
    For all Virtual Machines that have two or more instances deployed in the same Availability Set or in the same Dedicated Host Group, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.95% of the time.
  12. arjunyv2022 👍 1 Answered B
    the given solution only uses one Availability Zone, it does not meet the 99.99% availability requirement. The correct approach is to deploy the VMs across at least two Availability Zones.
  13. Said Ismail 👍 1 Answered B
    To achieve a 99.99% availability SLA in Azure, you need to deploy two virtual machines in separate availability zones within the same region
  14. wyabcp 👍 1 Answered B
    Answer is No - as you can get 99.99% with single VM and premium SSD

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