Carbon FAQs and Answers
5 min read
Common questions about Carbon.
Is there a trial?
Yes. Request a trial or demo from the product page. The Setup Wizard has a Request free trial key button if you do not have a key yet. For licensing pricing, contact sales@smikar.com.
Can I migrate a running Azure VM?
No. Carbon only migrates VMs that are Stopped (deallocated) in Azure. Running VMs cannot be replicated - you must stop and deallocate the source VM in the Azure portal before the migration. Plan a maintenance window that includes the downtime: stop → migrate → validate.
Does the Azure source VM get deleted?
No. Carbon reads the source VM but never modifies or deletes it. The Azure resource remains intact (Stopped / deallocated, since you stopped it before migration) until you decide to delete it manually. Many teams keep the Azure source for a rollback period - see Post-migration checks.
What target hypervisors can I migrate to?
Four options:
- VMware vSphere via vCenter - typical enterprise VMware estates. Needs a service account with specific vCenter privileges.
- 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 can be added in one Setup Wizard pass.
- Microsoft Hyper-V via SCVMM - centrally-managed Hyper-V environments.
You pick the target during the Setup Wizard; multiple target environments can be configured.
Does it need an agent on the source VM?
No. Carbon talks to the Azure management plane and the source VM's disks via Azure APIs. The source VM is not touched directly.
What permissions does it need in Azure?
The Azure account used in the Setup Wizard needs Owner on the source subscriptions, or equivalent RBAC for VM and storage resource management. Owner is the simplest grant; narrower scoping works as long as the account can read VM configuration, read disk content, and enumerate subscriptions.
What permissions does it need in vCenter?
The vCenter service account needs a specific set of privileges spanning datastore operations, network configuration, resource management, VM configuration, inventory management, VM interactions, and provisioning. See VMware permissions reference for the exact list and a recommended role-setup procedure.
How long does a migration take?
Bounded by network bandwidth between Azure and your on-premises environment, plus the source VM disk size. As a rough guide:
- Small VMs (under 100 GB total disks) - tens of minutes on a healthy network.
- Medium VMs (a few hundred GB) - a few hours.
- Large VMs (TB-scale) - many hours, possibly overnight.
ExpressRoute or a fat site-to-site VPN make the biggest difference. Public-internet bandwidth limits big migrations.
Why does Carbon need disk space locally?
Carbon downloads the source disks from Azure to the Carbon machine, converts them to the target format (VMDK for VMware, VHD for Hyper-V), then pushes the converted disks to the target datastore. The Carbon machine acts as the conversion staging point - you need enough free disk space on it to hold the largest VM you plan to migrate (decompressed).
Can I batch-migrate many VMs at once?
Yes. Multi-select VMs in the main view and Carbon runs them in parallel up to a worker concurrency limit. All selected VMs must be Stopped (deallocated). See Migrate a VM for the batch workflow.
What happens if a migration fails partway through?
The partially-transferred target VM is removed; the source Azure VM is unaffected; Carbon emails a failure notification if you have notifications configured. You can re-run the migration after addressing the cause (most commonly bandwidth interruptions, target-datastore-full, expired credentials, or the source VM accidentally being left in Running state).
Will the migrated VM have the same IP?
The migrated VM gets a new IP on the target network - typically allocated by your on-premises DHCP or assigned static by the network team. Plan for IP changes when you migrate; update DNS, firewall rules, and dependent systems accordingly.
Does it migrate Azure managed identities, RBAC roles, or tags?
No - these are Azure-specific concepts that have no equivalent on-premises. The migrated VM has the same OS, applications, and disk content but you will need to re-implement equivalent identity and access controls in your on-premises environment.
How is Carbon different from Azure Site Recovery (ASR)?
Azure Site Recovery is Microsoft's tool for replicating VMs between Azure and on-premises for disaster recovery and migration. ASR primarily targets on-premises to Azure (the forward direction). Carbon is purpose-built for the reverse - Azure back to on-premises - with a workflow optimised for repatriation. Customers who need bidirectional capabilities often use both: ASR for inbound, Carbon for outbound.
How do I uninstall Carbon?
Windows Settings → Apps → Carbon → Uninstall. No Azure-side cleanup is required - Carbon does not register an application in Entra ID for its operation (it uses your direct sign-in credentials during the Setup Wizard).
Need help? support@smikar.com.