Is there any way to have VMs of different sizes in the private agents pool of an Azure Container Service (ACS)? I would like to support use cases where some services require compute intensive servers and others (e.g databases) memory intensive servers.
An acceptable solution could be to add multiple virtual machines scale sets (vmss) as private agents pools and each one of them have VMs of different sizes since a vmss supports one size of VM. Is such a feature supported in ACS?
A workaround could be to have different sizes of VMs in the public and private agent pools. However, this is not a best practice since public agents pool should be used to host services that are exposed publicly (e.g marathon-lb). Also, it limits the options to just two pools.
This feature is coming and if you need them today you can use ACS Engine (the open source code behind ACS). See examples at https://github.com/Azure/acs-engine/tree/master/examples/largeclusters
Related
I know that Azure Isolated App Service Plan provide several benefits like:
Network level isolation
More worker units
Better performance
but i wonder if the isolation is also on the hardware level or not ?
With Azure App Service Environment version 3 (ASEv3), you can deploy it on a dedicated host group. Host group deployments are not zone redundant for ASEv3.
Azure Dedicated Host is a service that provides physical servers - able to host one or more virtual machines - dedicated to one Azure subscription. Dedicated hosts are the same physical servers used in our data centers, provided as a resource. You can provision dedicated hosts within a region, availability zone, and fault domain. Then, you can place VMs directly into your provisioned hosts, in whatever configuration best meets your needs.
This is NOT available with ASEv2.
Reference:
https://learn.microsoft.com/en-us/azure/app-service/environment/overview
https://learn.microsoft.com/en-us/azure/virtual-machines/dedicated-hosts
I am basically looking a brief explanation on when to choose Azure scale sets and Azure Virtual Host pools.
You create Azure VM Scale Sets when you want to build large-scale services that are highly available. Using VM scale sets would let you create and manage a group of load balanced VMs and maintain a consistent configuration across all instances.
Scale sets can automatically increase the number of VM instances as application demand increases, then reduce the number of VM instances as demand decreases. This ability helps reduce costs and efficiently create Azure resources as required matching your customer demand.
#mmking is right in that Host pools are specific to WVD. Host pools are like a collection of identical virtual machines within Windows Virtual Desktop environments.
Additional resources:
Virtual machine scale sets
WVD host pools
I am having difficulty understanding Azure Availability sets, specifically, what exactly i need to to do ensure my app running on my vm is utilizing Availability sets to be more available.
Lets say i am creating an application that runs on a single VM and i want to make it more resistant to hardware failure.
Option 1:
I create an Availability Set with 2 fault domains and then create a VM on this Availability set.
Is that it?
If there is a hardware failure on the rack hosting my VM, does azure now take care of ensuring the VM stays up and running?
Option 2:
i have to have two servers Vm1 & Vm2, both in the availability set but one on fault domain 1, one on fault domain 2.
i have to then set up a cluster of sorts for my application. In this case the availability set is simply allowing me to be sure that the two servers in my cluster are not on the same hardware, but the plumbing to ensure the application can take advantage of two servers and is highly available is still down to me.
Is option 1 or option 2 the correct way in which Availability Sets work in relation to fault domains?
Appreciate any clarity that can be provided.
Azure deals with hardware failure in two ways, Availability Sets and Availability Zones. AS is all about making sure that your app does not go down even if hardware failure happens within a Data center aka Zone itself. AZs are all about making sure your app does not go down even if the whole data center aka Zone is down. More details here.
Now to understand best practices around availability take a look at the best practices, specifically for VMs can be found here.
A Single VM instance is defined as follows, reference:
"Single Instance" is defined as any single Microsoft Azure Virtual Machine that either is not deployed in an Availability Set or has only one instance deployed in an Availability Set.
So one VM in or not in an availability set does not make any difference, for this you need at least two VMs and which are in an AS using FDs and UDs so Azure will take care of this by making sure that both VMs are running on separate Hardware to avoid your app going down.
One VM in an Availability set is nearly as good as a VM with no Availability set.
If you are placing two or more VMs in an AS and those are identical then you can add a load balancer to distribute traffic.
You can also use AS without a Load balancer if you are not interested in traffic distribution. One scenario can be where you want to switch to a secondary VM only when primary is unavailable.
Also, do understand it is not required to have identical VMs in an AS.
Virtual machine scale set is a good option if you are looking for a high availability solution with VMs.
Our issue:
The amount of time for provisioning a new instance takes a long time because of steps like certificate, encryption, domain join, TLS and Cipher changes,...
Solution:
In our use case, we end up to have two different VMSS for the purpose of deployment, re-imaging or blue green use case. Please note in our region (Azure Gov), we don't have access to low priority VMSS or Azure VM Spot to do pre-provisioning.
It only makes sense to have two different scales set behind a cloud-native load balancer (or private Traffic Manager - which is not available yet) to route request base on the VMSS prob readiness.
Ask:
How can we have two Azure Virtual Machine Scale Set behind a load balancer
I never tried this, but I dont see why this would not work with Standard Load Balancer (not basic, basic one is limited to 1 vmss, afair), if it doesnt - it should work with Application Gateway.
We have a standard 3 tier web application that need to be migrated into cloud (more of VM based lift and shift instead of cloud native at this point).
Wondering which factors should I consider to make a decision if Azure Scale Set or Azure Availability Set should be used for Web and Application tiers.
Probably answer to questions like:
Can availability set autoscale like Scale set?
Any overhead of using either option for a simple web application?
Will both need load balancer in front of them ?
Might help to take a decision.
Any suggestions please?
You can refer to the N-tier architecture on virtual machines. Each of tier consists of two or more VMs, placed in an availability set or VM scale set. The load balancer is used to distribute requests across the VMs in a tier. Each tier is also placed inside its own subnet, and add NSG rules to restrict access to each tier and route tables to individual tiers.
For your questions:
No, The main difference is that a Scale Set have Identical VMs which makes it easy to add or remove VMs from the set whereas an Availability Set does not require them to be identical. An availability set is spread across fault domains that shared a set of hardware components, which means when you have more than one VM in different fault domains in a set it reduces the chances of losing all your VMs in event of a hardware failure in the host or rack. A regional (non-zonal) scale set uses placement groups, which act as an implicit availability set with five fault domains and five update domains. Refer to this question.
It's recommended to use VM Scale Sets for autoscaling. VMSS can automatically create and integrate with the Azure load balancer or Application Gateway.
Yes, both need Azure LB in front of them.
Generally speaking, both scenarios do not offer any way to magically make this happen, so you are kinda forced to use webapps if you want minimum overhead.
yes it can, but you need to prestage vms
yeah, you need to configure vms and for vmss you need automation so that scaling can happen automatically
yes, both will need a load balancer (web apps - not).
But your app might not work with webapps, so you are kinda forced to use vms or vmsses