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Feature Analysis: Cloud Services (extended support) and Virtual Machine Scale Sets

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This article provides a feature analysis of Cloud Services (extended support) and Virtual Machine Scale Sets. For more information on Virtual Machine Scale Sets, please visit the documentation here

Basic setup

Feature CSES Virtual Machine Scale Sets (Flex) Virtual Machine Scale Sets (Uniform)
Virtual machine type Basic Azure PaaS VM (Microsoft.compute/cloudServices) Standard Azure IaaS VM (Microsoft.compute/virtualmachines) Scale Set specific VMs (Microsoft.compute /virtualmachinescalesets/virtualmachines)
Maximum Instance Count (with FD guarantees) 1100 1000 3000 (1000 per Availability Zone)
SKUs supported D, Dv2, Dv3, Dav4 series, Ev3, Eav4 series, G series, H series D series, E series, F series, A series, B series, Intel, AMD; Specialty SKUs (G, H, L, M, N) are not supported All SKUs
Full control over VM, NICs, Disks Limited control over NICs and VM via CS-ES APIs. No support for Disks Yes Limited control with virtual machine scale sets VM API
RBAC Permissions Required Compute Virtual Machine Scale Sets Write, Compute VM Write, Network Compute Virtual Machine Scale Sets Write, Compute VM Write, Network Compute Virtual Machine Scale Sets Write
Accelerated networking No Yes Yes
Spot instances and pricing No Yes, you can have both Spot and Regular priority instances Yes, instances must either be all Spot or all Regular
Mix operating systems Extremely limited Windows support Yes, Linux and Windows can reside in the same Flexible scale set No, instances are the same operating system
Disk Types No Disk Support Managed disks only, all storage types Managed and unmanaged disks, All Storage Types
Disk Server Side Encryption with Customer Managed Keys No Yes
Write Accelerator No No Yes
Proximity Placement Groups No Yes, read Proximity Placement Groups documentation Yes
Azure Dedicated Hosts No No Yes
Managed Identity No User Assigned Identity Only System Assigned or User Assigned
Azure Instance Metadata Service No Yes Yes
Add/remove existing VM to the group No No No
Service Fabric No No Yes
Azure Kubernetes Service (AKS) / AKE No No Yes
UserData No Yes Yes

Autoscaling and instance orchestration

Feature Cloud Services (extended Support) Virtual Machine Scale Sets (Flex) Virtual Machine Scale Sets (Uniform)
List VMs in Set No Yes Yes
Automatic Scaling (manual, metrics based, schedule based) Yes Yes Yes
Auto-Remove NICs and Disks when deleting VM instances Yes Yes Yes
Upgrade Policy (VM scale sets) AutoUD and ManualUD policies. No support for Rolling. Cloud Services - Create Or Update - REST API (Azure Compute) No, upgrade policy must be null or [] during create Automatic, Rolling, Manual
Automatic OS Updates Yes No Yes
Customer Defined OS Images No Yes Yes
In Guest Security Patching No Yes No
Terminate Notifications (VM scale sets) No Yes, read Terminate Notifications documentation Yes
Monitor Application Health No Application health extension Application health extension or Azure Load balancer probe
Instance Repair (VM scale sets) No Yes, read Instance Repair documentation Yes
Instance Protection No No, use Azure resource lock Yes
Scale In Policy No No Yes
Get Instance View Yes No Yes
VM Batch Operations (Start all, Stop all, delete subset, etc.) Yes Partial, Batch delete is supported. Other operations can be triggered on each instance using VM API) Yes

High availability

Feature Cloud Services (extended Support) Virtual Machine Scale Sets (Flex) Virtual Machine Scale Sets (Uniform)
Availability SLA SLA SLA SLA
Availability Zones No Specify instances land across 1, 2 or 3 availability zones Specify instances land across 1, 2 or 3 availability zones
Assign VM to a Specific Availability Zone No Yes No
Fault Domain – Max Spreading (Azure will maximally spread instances) Yes Yes Yes
Fault Domain – Fixed Spreading 5 update domains 2-3 FDs (depending on regional maximum FD Count); 1 for zonal deployments 2, 3 5 FDs 1, 5 for zonal deployments
Assign VM to a Specific Fault Domain No Yes No
Update Domains Yes Depreciated (platform maintenance performed FD by FD) 5 update domains
Perform Maintenance No Trigger maintenance on each instance using VM API Yes
VM Deallocation No Yes Yes

Networking

Feature Cloud Services (extended Support) Virtual Machine Scale Sets (Flex) Virtual Machine Scale Sets (Uniform)
Default outbound connectivity Yes No, must have explicit outbound connectivity Yes
Azure Load Balancer Standard SKU No Yes Yes
Application Gateway No Yes Yes
Infiniband Networking No No Yes, single placement group only
Azure Load Balancer Basic SKU Yes No Yes
Network Port Forwarding Yes (NAT Pool for role instance input endpoints) Yes (NAT Rules for individual instances) Yes (NAT Pool)
Edge Sites No Yes Yes
Ipv6 Support No Yes Yes
Internal Load Balancer No Yes Yes

Backup and recovery

Feature Cloud Services (extended Support) Virtual Machine Scale Sets (Flex) Virtual Machine Scale Sets (Uniform)
Azure Backup No Yes No
Azure Site Recovery No Yes (via PowerShell) No
Azure Alerts Yes Yes Yes
VM Insights No Can be installed into individual VMs Yes

Next steps