What is the Azure SLA for two or more virtual machines in an availability set?

In this video-blog, we are about to cover Microsoft Azure’s most important concepts like Azure Availability Zones, Region, Availability Set, Fault Domain, and Update Domain In Azure, and how it plays a key role in Virtual Machines.

Note: Also read our previous blog on What is Resource Group and How to Create Resource Group.

The basic Architecture of the Azure can easily be understood by the following diagram

Azure Region

A region is a set of data centers deployed within a latency-defined perimeter and connected through a dedicated regional low-latency network.

With more global regions than any other cloud provider, Azure gives customers the flexibility to deploy applications where they need to. Azure is generally available in 52 regions around the world, with plans announced for 6 additional regions.

Also read: Everything you need to know on Azure SQL Database

List of Azure regions with availability zones

Azure provides the foremost extensive global footprint of any cloud provider and is rapidly opening new regions and availability zones. the subsequent regions currently support availability zones.

AmericasEuropeMiddle EastAfricaAsia PacificBrazil SouthFrance CentralQatar Central*South Africa NorthAustralia EastCanada CentralGermany West CentralUAE North*Central IndiaCentral USNorth EuropeJapan EastEast USNorway EastKorea CentralEast US 2UK SouthSoutheast AsiaSouth Central USWest EuropeEast AsiaUS Gov VirginiaSweden CentralChina North 3West US 2Switzerland NorthWest US 3

Microsoft Azure Data Center Locations

Microsoft Azure currently has 59 regions operative and an additional 19 under development, meaning that the corporate will have a complete of 78 regions available within the near-term. Within each Azure region are 1 to three unique physical locations, referred to as availability zones, which provide high uptime to safeguard data and applications from data center failures.

Presently, Microsoft Azure has 113 availability zones operational and an additional 51 under development, meaning that the corporate will have a complete of 164 availability zones existing within the near-term.

Each Microsoft Azure availability zone is created from one or more data centers equipped with independent power, cooling, and networking. The physical separation of availability zones within a neighborhood protects applications and data from facility-level disruptions.

Benefits of a Direct Connection to Azure Locations

Layer 3 connectivity between your on-premises network and therefore the Microsoft Cloud through a connectivity provider. Connectivity is from an any-to-any (IPVPN) network, a point-to-point Ethernet connection, or through a virtual cross-connection via an Ethernet exchange.
Connectivity to Microsoft cloud services across all regions within the geopolitical region.
Global connectivity to Microsoft Azure services across all regions with the ExpressRoute premium add-on.
Dynamic routing between your network and Azure Microsoft via BGP.
Built-in redundancy in every peering location for higher reliability.
Connection uptime SLA.
QoS support for Skype for Business.

What is Region Pairing?

The reason I start here is that Azure contains a feature that’s unique among the large three cloud providers. It’s the concept of “region pairing.” Region pairing is that the relationship between two Azure regions within an identical geographical area to supply geographically redundant solutions. Azure’s paired regions are prewired with high bandwidth connectivity between them.

Azure operates in several geographies worldwide, and within given geography or geopolitical boundary, each region is deployed together with another paired region. Some exceptions exist, like Brazil, which is paired with South Central US, but these are edge cases. So, for instance, in the US, Microsoft pairs Virginia (called East US 2) with Iowa (called Central US). So, if you’re in East US 2 and a disaster recovery (DR) failover has to occur, you’re still within inexpensive proximity to your secondary region and warranted of a high level of service from a latency perspective. Contrast this with the first Virginia region, East US, which pairs with West US (California), and you’re faced with a far higher latency should your environment have to failover.

Region Pairs

Each Azure region pairs with another region within the same geography, together making a regional pair.
Azure serializes platform updates so only one region is updated at a time.
Azure Regions in a Pair have direct connections that bring additional benefits to use them together.
Each Azure Region in a pair is always located greater than 300 miles apart when possible.
Examples of region pairs are West US paired with East US, South-East Asia paired with East Asia.

Also check: Steps to register Azure Free Account

Geographies

Geography is a discrete market, typically containing two or more regions, that preserves data residency and compliance boundaries.

It allows customers with specific data-residency and compliance needs to keep their data and applications close. However, they are fault-tolerant to withstand complete region failure through their connection to our dedicated high-capacity networking infrastructure.

To know more about the Geography locations refer here

Also check: Step by Step instructions to install Azure Powershell module

Azure Availability Zone

Azure Availability Zones is a high-availability offering that protects your applications and data from datacenter failures.
These are unique physical locations within an Azure region. Each zone is made up of one or more data centers equipped with independent power, cooling, and networking.
The physical separation of Availability Zones within a region protects applications and data from datacenter failures.
Zone-redundant services replicate your applications and data across Azure Zones to protect from single-points-of-failure.
Not every region has support for Availability Zone Azure. The examples of Availability Zones are Central US, East US 2, West US 2, West Europe, France Central, North Europe & Southeast Asia
With Availability Zones, Azure offers industry best 99.99% VM uptime SLA(Service Level Agreement)

To achieve comprehensive business continuity on Azure, build your application architecture using the combination of Azure Zones with Azure region pairs.

Also read: Complete Guide on AZ 103 Exam

Azure Availability Set

An Availability Set is a logical grouping capability for isolating VM resources from each other when they’re deployed.
By deploying your VMs across multiple hardware nodes Azure ensures that if hardware or software failure happens within Azure, only a sub-set of your virtual machines is impacted and your overall solution is safe and in working condition.
It provides redundancy for your virtual machines.
An Availability set spreads your virtual machines across multiple fault domains and update domains.
If you want to leverage Microsoft’s 99.95% SLA from Microsoft you must place your VMs inside availability set except your VMs are having premium storage.

An Update Domain and Fault Domain is assigned to each VM in Availability Set by Azure platform.

To know more about the az 104 Microsoft Azure Administrator certification exam. Click here

Availability Set vs Availability Zone

Availability Sets takes the virtual machine and configures multiple copies of it. Each copy is isolated within a separate physical server, compute rack, storage units and network switches within one datacentre within an Azure Region.
When you create your virtual machine you’ll be able to specify the provision Set, you can’t change it or move it in or out of an Availability Set after creation. If you wanted to create changes you’d start again and recreate the virtual machine. And Availability Sets only apply to virtual machines, they can’t be used for the other kind of resources within Azure.
Using an Availability Set takes your acceptable downtime to around 22minutes a month. Which could be a vast improvement over the one virtual machine deployment.

The next level of availability for your virtual machines within Azure is Availability Zones. With Availability Zones utilised your acceptable downtime a month moves to but 5 minutes as you’ve got a 99.99% SLA.

With Availability Zones, you’re setting out to use zone-aware services. Your workload is opened up across the various zones that compose an Azure region. An Azure region is formed from multiple datacentres and every zone is formed from one or more datacentres. Each datacentre is provided with independent power, cooling and networking.

When should I use an Available Zone vs Set?

When building your workload in Azure it’s important you concentrate on carefully how you’re to create availability in your virtual machine infrastructure. There are some factors you ought to consider when choosing whether to use availability sets or zones.

Cost

When creating an availability zone there’s a further bandwidth cost for data moving into and out of a zone. it’s however quite minimal, at around 1 pence per GB, but it quickly builds up with workloads that have a high data churn.

Storage

Where availability zones support managed disks, availability sets don’t directly. This doesn’t mean that managed disks that are attached to VMs in availability sets don’t seem to be as available, they’re still provisioned in such how that they’re isolated from one point of failure. Whereas in the availability zone, a duplicate of that managed disk is found inside each zone.

Availability

As availability sets and availability zones are two different services, they both include different SLA (service level agreements). The SLA is defined as a percentage, as specifies the guaranteed uptime of your compute or service. This doesn’t include your application or overall workload, but the underlying azure service running it. Where availability sets guarantee a 99.95% uptime, availability zones guarantee a 99.99% uptime. Although this doesn’t appear to if much, this (on paper) is the difference between around 5 hours of cumulative downtime over one year compared to under 1 hour of cumulative downtime.

Microsoft Azure’s regions vs. Amazon Availability Zones

For most customers, the differences between these approaches won’t matter an excessive amount of, says Jared Wray, former CTO of CenturyLink’s cloud and now an entrepreneur. He says the foremost common deployment method for enterprise apps migrating to the cloud is to host them in one region and back it up to a different (an active-passive setup). In AWS’s case, is done to bushed one region across two AZs. In Microsoft or Google’s case, another region would be used. Cloud providers offer ok latency across their regions for many workloads, Wray says.

Where AZ’s shine, he notes, is that if you wish a low-latency backup or an active-active backup. AZs within the identical region have fast dedicated connections, which are ideal for these apps.

AZs include some downsides though, Wray adds. If an AZ has an outage, many purchasers have designed their workloads failover to a different AZ in this same region. If all of the purchasers within the downed AZ transfer workloads to the healthy AZ, that would theoretically create a crowded AZ, which could impact performance.

To help alleviate this issue, cloud vendors are continually adding new regions. Just this month Amazon launched a replacement region in Ohio to assist offload capacity from its Virginia region and satisfy increased demand for its services. Microsoft brought on two new government regions this month too.

At the tip of the day, for many customers, the AZ vs. region debate will likely not be a deciding factor in which cloud provider to travel with. sure enough customers, it may well be an enormous factor reckoning on how latency-sensitive the backup of the app must come online. Either way, it’s certainly are a few things to a minimum remembering.

Azure Fault Domains

Azure Fault domains define the group of virtual machines that share a common power source and network switch.
Each and every fault domain contains some racks and each rack contains a virtual machine.
Each of these Azure Fault domains shares a power supply and a network switch.
All the resources in the fault domain become unavailable when there is a failure in the fault domain.
You should place your VMs in such a way that each fault domain gets one web server, one database server, and like that.

Azure Update Domain

Virtual machines get updated domains automatically once they are put inside the availability set.
All virtual machines within that update domain will reboot together.
They are used for patching of the virtual machines.
Only one updated domain can be updated at a time.

Check Out: What is Azure Virtual Machine Scale Set?

How many Fault Domains and How many Update Domains we can have?

In the Azure Service Management (ASM) portal, we have two Fault domains and 5 update domains.
In the Azure Resource Manager(ARM) portal, we have three Fault domains and 5 update domains but we can upgrade our update domains from 5 to 20.
VMs are assigned sequentially in the update domains and fault domains.

Key Points To Remember

You need to create virtual machines in the same resource group as the availability set.
Only one virtual machine can only be in one availability set.
Virtual machines can be assigned availability set only during their creation of it.

Check Out: Azure load balancer vs Application Gateway: know their major differences!

SLA(Service Level Agreement) for VM:

For all Virtual Machines that have two or more instances deployed in the same Availability Set, Azure guarantees 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 storage for all disks, Azure guarantees you will have Virtual Machine Connectivity of at least 99.9%.

Also Read: Our previous blog post on Azure Blob Storage. Click here

Hope the blog will help you in understanding the concepts of Region, Availability Zone, Availability Set, Fault Domain, and Update Domain, and how it plays a key role in Virtual Machines. Now it’s your turn to post your doubts in the comment section.

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