Backup Software: Agent vs Agentless – Which Solution is Better for Your IT Environment?
Introduction
Choosing between agent-based and agentless backup software can significantly impact your IT infrastructure’s performance, complexity, and cost.
This guide explains the key differences, advantages, and best practices for each method—helping you determine which backup strategy suits your VMware, Hyper-V, or cloud environment best.
Virtualization technology is a revolutionary force in the IT world. Similarly, in the backup domain, the concept of agentless backup, introduced with the adoption of virtualization, continues to challenge traditional technologies. However, as a pair of contradictory technologies—agent-based backup and agentless backup—their respective advantages and disadvantages are quite pronounced. Yet, Veeam's agentless backup technology leverages the best of both worlds, achieving application awareness while performing agentless backups.
1. What Is Agent-Based Backup?
This IT term is difficult to define clearly and precisely, which often leads to ambiguity in our daily technical discussions. Sometimes we talk about agents in a broad sense, and other times in a narrow sense. I tried to find a definition on Baidu Baike but came up empty-handed. On Wikipedia, there is a definition for a Software Agent, but it only lists some characteristics that such an agent should possess based on a common understanding:
- Persistent Operation - Typically remains running, even when idle, staying in a wait state.
- Autonomous Operation - Can operate without human intervention or interaction.
- Application Interaction Capability - Can interact with other programs, activate other modules, communicate, and collaborate.
Upon closer reflection, the agent software used in traditional agent-based backup does indeed fit these characteristics of what an Agent should be.
An agent-based backup requires installing a small software agent inside every system you want to protect.
Advantages:
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Deep visibility into applications and operating systems.
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Ideal for databases, mail servers, and legacy systems.
Disadvantages:
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Higher maintenance and update complexity.
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Increased CPU and memory overhead on each host.
📌 Example: Veeam Agent for Windows is a common solution for granular physical or endpoint protection (Veeam Docs).
2. What Is Agentless Backup?
Virtualization backup technology does not require installing any such programs within any operating system; therefore, backups do not depend on the system's running state.
Application awareness, on the other hand, involves automatically running a process within the operating system during the backup process to handle application awareness, ensure consistency, and manage file system consistency. It then closes the application and exits. This process is merely an optional step during backup execution and is entirely different from the aforementioned agent program.
Consequently, the problems typically faced by agent programs also apply to backup agents:
- You constantly need to manually install agent programs on newly deployed virtual machines (we consider push installations convenient, but they still count as a form of "manual" work, requiring remote or local configuration);
- During software updates, you need to upgrade the agent on every single machine.
- In large-scale, long-term operations, you also need to consider using some software to monitor these agents—what we call an "agent babysitter"—to ensure they don't suddenly stop working without anyone noticing;
- All of these consume computing resources—CPU, memory, network, storage—continuously, and often redundantly.
The process that backup software uses for application-level awareness runs for just a few minutes at the start of the backup and then immediately shuts down and exits. Therefore, it completely avoids all the issues mentioned above. No need for per-deployment installation, no updates, no long-running monitoring.
What's more interesting is that in today's IT world, the more you run, the greater the risk. When we have no applications running, we are in the safest possible state. Each additional application increases the risk of attack by hackers, viruses, or ransomware. Reducing the number of continuously running applications on each system adds a layer of security to our infrastructure.
Furthermore, if a system is shut down, an agent program that needs to be running to perform backups is completely useless. A backup target going offline is a common sight in traditional backup software interfaces. In such cases, the only thing a backup administrator can do is to find the application or infrastructure administrator to boot up the operating system. With agentless technology, backups remain unaffected even when the system is powered off. And during the restore process, the backup software's diverse granular recovery options can still be performed manually, making it a perfect solution for both backup and restore.
Agentless backup performs backups remotely without installing software on each system. It connects via APIs, hypervisor integrations, or remote protocols.
Advantages:
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Easier to deploy and manage across large environments.
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Less system impact and faster backups.
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Works perfectly for VMware, Hyper-V, and cloud workloads.
Disadvantages:
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Limited application-level recovery in some cases.
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May not capture OS-specific logs or configurations.
👉 Related reading: Free Backup for VMware and Hyper-V with Vinchin
3. More Drawbacks of Traditional Backup Agents
Data backups that utilize agent technology overwhelmingly rely on the network. When we design DMZ zones for security isolation and enforce strict inbound/outbound rules, we suddenly realize that to implement this backup insurance, we must have a data stream into the DMZ zone to extract data. This breaks the originally completely isolated architecture, undermining the carefully designed, perfect structure.
Agentless application insertion technology is completely different from traditional agents. When performing application awareness, this execution can be carried out at the hypervisor level via VIX without requiring network connectivity. Therefore, in the design philosophy of backup software, it can bring an extra layer of security to backups in DMZ zones.
4. Which Backup Type Should You Choose?
| Environment | Recommended Method | Why |
|---|---|---|
| Virtual Machines (VMware/Hyper-V) | Agentless | Easy to manage, faster |
| Physical Servers | Agent-based | Better for app-level consistency |
| Cloud Workloads | Agentless (API-based) | Scalable, cost-efficient |
| Legacy Systems | Agent-based | Required for deeper integration |
5. Combining Both for Best Results
A hybrid approach can deliver the best of both worlds:
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Use agentless backup for general VM protection.
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Deploy agents only where necessary (e.g., databases, ERP systems).
This approach simplifies management while maintaining granular recovery capabilities.
📖 For additional insights, see Gartner’s Data Protection Market Guide on backup technologies and trends.
Conclusion
The debate between agent vs agentless backup software isn’t about which is universally better—it’s about choosing what fits your infrastructure.
For large-scale VMware and Hyper-V environments, agentless backup provides simplicity and scalability. Meanwhile, agent-based backup remains vital for detailed application-level restores.
By understanding both approaches, you can design a balanced data protection strategy that ensures reliability, performance, and compliance.