The number of virtual machines does not matter for licensing. Each installation needs a license.
If you are using Hyper-V on Windows 8 instead of a Windows Server 2008 or later, you can back up Windows 8 Hyper-V with a Professional Edition, provided that you do not use Hyper-V checkpoints / snapshots.
For four hosts you hence need just four licenses.
Backup Software OverviewThe Best Backup Software in 2022 Download BackupChain®
BackupChain Backup Software is the all-in-one Windows Server backup solution and includes:
Disk Image Backup
Drive Cloning and Disk Copy
File Server Backup
Virtual Machine Backup
Server Backup Solution
- Best Practices for Server Backups
- NAS Backup: Buffalo, Drobo, Synology
- Cloud Backup Solution for Windows Server
- DriveMaker: Map FTP, SFTP, S3 Sites to a Drive Letter (Freeware)
- VM Backup
- Knowledge Base
- BackupChain (German)
- German Help Pages
- BackupChain (Greek)
- BackupChain (Spanish)
- BackupChain (French)
- BackupChain (Dutch)
- BackupChain (Italian)
- BackupChain is an all-in-one, reliable backup solution for Windows and Hyper-V that is more affordable than Veeam, Acronis, and Altaro.