Getting Started with Carbon

5 min read

Carbon is a Smikar Software tool for migrating Azure virtual machines back to on-premises hypervisors. If your organisation has decided that some Azure workloads should run on-premises again - for cost, performance, sovereignty, regulatory, or strategic reasons - Carbon automates the VM discovery, conversion, and configuration.

This page is the orientation: what Carbon does, who it's for, why customers use it, supported targets, and the reading order to follow.

What Carbon does

Carbon connects to your Azure subscriptions, lists the VMs with detailed metadata (name, status, size, CPU count, memory, IP address, VNET, operating system, resource group, subscription, location), and lets you select one or many for migration to an on-premises VMware or Hyper-V environment. The migration pipeline has four phases:

VM discovery and assessment - Carbon enumerates Azure VMs across connected subscriptions and gives you the full picture before any migration starts.
Replication and conversion - selected VMs are replicated to the target hypervisor with format conversion (VHD ↔ VMDK) as required.
Configuration - the new VM is set up with the same CPU, memory, and disk configuration as the Azure source.
Monitoring - automatic email notifications alert you to status changes during the migration.

The source Azure VM is never modified or deleted by Carbon - the migration is one-way replication that leaves the original intact for rollback or staged cut-over.

Important constraint

Carbon migrates only stopped (deallocated) Azure VMs. Running VMs cannot be migrated - you must stop and deallocate the source VM in Azure before Carbon can replicate it.

Plan migration windows that accommodate the planned downtime: stop the Azure VM, run the Carbon migration, validate the on-premises VM, optionally start the Azure VM as a rollback if anything is wrong.

Why customers use Carbon

The repatriation thesis - moving workloads back from cloud to on-premises - is increasingly mainstream. Five drivers come up consistently:

Cost - Azure operating costs can exceed equivalent on-premises costs for stable, predictable workloads where elastic scaling does not pay off.
Performance - workloads with heavy data processing, low-latency requirements, or specific geographic-market needs can perform better on infrastructure you control.
Regulatory and data sovereignty - having data in a data centre your organisation controls is reassuring for regulated industries (healthcare, finance, government) and for jurisdictions where data residency rules apply.
Control and security - on-premises environments give complete control over where data is stored, who can access it, and how it is protected. For sensitive workloads, that control matters.
Strategic autonomy - de-clouding lets organisations align IT strategy to business objectives without conforming operations to a single cloud provider's constraints.

If one or more of these apply to specific workloads in your Azure estate, Carbon is the tool that automates the move.

Who it's for

IT teams moving workloads back from Azure to on-premises in response to cost reviews.
Migration planners consolidating cloud and on-premises estates.
Architects repatriating specific workloads where on-premises is the right home (latency-sensitive applications, regulated data, specialised hardware requirements).
Finance teams working with IT to reduce ongoing Azure spend by moving long-lived, predictable workloads off the cloud.

Carbon is purpose-built for the Azure-to-on-premises direction. For the reverse (on-premises to Azure), Microsoft's Azure Site Recovery is the standard tool.

Supported source and target

Source: Microsoft Azure VMs across any subscription your sign-in account can read.

Target on-premises hypervisors - four options:

VMware vSphere via vCenter - typical enterprise VMware estates.
VMware ESXi (direct) - standalone ESXi hosts without vCenter. SSH must be enabled on the host.
Microsoft Hyper-V (without SCVMM) - direct Hyper-V host connection, up to 10 hosts.
Microsoft Hyper-V via SCVMM - centrally-managed Hyper-V environments.

What you need

A Windows machine for the Carbon console - workstation or server.
Local admin rights on that machine (the installer needs UAC approval for prerequisite installs).
An Azure account with Owner (or equivalent RBAC for VM and storage resource management) on the source subscriptions.
Credentials and network access to your target hypervisor environment.
For VMware vCenter targets: a service account with the exact privileges listed in the VMware permissions reference.
For VMware ESXi direct targets: SSH enabled on the host.
For Hyper-V targets: Hyper-V Management Tools with PowerShell module installed on the Carbon machine.
Sufficient network bandwidth between Azure and on-premises. Migration time is bounded by disk transfer; ExpressRoute or a sized site-to-site VPN make a meaningful difference for large workloads.
Sufficient disk space on the Carbon machine for VMware conversions (Carbon downloads disks and converts to VMDK locally before pushing to the target).
Target datastore with enough free space for the migrated VM disks.