Recovering an entire virtual machine and retrieving a database object are different jobs. Your backup approach should support the recovery your team needs, at a level of administration it can sustain as VM counts grow.
Agent-based backup puts backup software inside the guest operating system. Agentless backup works through the virtualization platform, reducing the number of guest backup agents to maintain. This guide compares the trade-offs, using Catalogic DPX examples to show where each approach fits.
What Agent-Based and Agentless Backup Mean
A virtual machine runs its own operating system on hardware managed by a hypervisor. A guest backup agent works inside that operating system, where it can access supported applications and their data. Each protected guest needs the appropriate agent installation and configuration.
Agentless backup captures VM data through the hypervisor’s interfaces. The backup product still needs supporting infrastructure. In DPX VMware protection, a virtualization proxy reads data through VMware’s backup APIs; the protected guests do not need a DPX backup agent. VMware Tools is required inside the guest for the documented application-quiescing workflow.
The host components differ on other platforms. DPX Hyper-V backup uses a backup agent on the Hyper-V host. Proxmox VE backup uses the Proxmox API and a DPX host plugin to protect QEMU VMs. These designs avoid a backup agent in each guest, while keeping platform-specific requirements.
Agent-Based Backup for Application-Level Recovery
Guest agents are useful when an application needs its own protection and recovery workflow. In DPX, application-aware Block Data Protection uses the DPX Client inside the VM. The application protection documentation distinguishes this from agentless VMware backup and recommends it where granular application recovery or direct storage access is required.
That distinction matters when recovering an entire VM would disrupt more work than necessary. If the incident calls for an application-level restore, confirm that the backup mode supports the exact operation you need. File recovery and database-object recovery are separate capabilities.
Maintenance and Resource Use
Guest agents need configuration and updates throughout the VM’s life. Include that work in the deployment plan, especially where teams create and retire VMs frequently. Check support for each guest operating system and application version.
Backup processing also uses resources. Measure its effect during a representative backup window rather than assuming every agent consumes excessive CPU or memory. Total cost depends on the licensing model and infrastructure as well as the time spent maintaining protection.
Installing an agent does not by itself guarantee application consistency or improve security. Supported application integration and successful backup processing determine consistency. Security depends on access controls and the protection of retained recovery copies under either approach.
Agentless Backup with Fewer Guest Agents to Maintain
Agentless protection reduces the work of installing and updating backup software inside individual VMs. For a large virtual estate, managing protection through the hypervisor can make routine administration easier. Proxy or host components still need maintenance and sufficient resources for the backup workload.
DPX uses Changed Block Tracking (CBT) for incremental VMware backups after the initial base backup. The backup architecture guide explains the transport modes and disk restrictions. Test throughput against your backup window instead of treating agentless operation as a performance guarantee.
Application Consistency Is Available
DPX can create application-consistent agentless VMware backups for supported VSS-aware Windows applications. This requires VMware Tools in the guest and the file system and application quiesce option enabled. Microsoft VSS coordinates the application state before the snapshot is taken. Without quiescing, the documented workflow produces a crash-consistent backup, which can omit transactions still in memory.
See DPX application-consistent protection for the requirements. Validate quiescing and restore the application during testing. The VMware workflow should not be assumed to apply unchanged to another hypervisor or application.
File Recovery Is Also Available
With DPX, agentless VMware and Hyper-V backups stored on vStor support recovery of individual files or directories. You can retrieve missing data without restoring the whole VM. The Agentless File Restore guide lists the requirements; ReFS, Btrfs and LVM are excluded from mounting in this workflow.
A VM image can support file recovery while a particular application-object restore still requires an application-aware backup. Confirm the recovery object you need when evaluating either approach.
Discovery Needs a Working Backup Policy
Seeing a VM in the inventory is only the start of protection. In DPX VMware backup, job configuration defines the source selection and destination, with a schedule for recurring runs. Review job scope when VMs are added or moved, then check that jobs run successfully and retain usable recovery points.
DPX provides an option to fail a job when an unsupported VM or disk is skipped, so exclusions can be made visible rather than mistaken for complete coverage.
Compare the Recovery You Need
The following comparison uses DPX VMware protection. Exact support depends on the backup mode and the application’s requirements.
| Requirement | Guest-agent approach | Agentless VMware approach |
|---|---|---|
| Guest software | DPX Client in protected guests | No guest DPX backup agent; VMware Tools for quiescing |
| Application consistency | Supported application-aware protection must be configured | Supported VSS-aware applications with VMware Tools and quiescing |
| Individual files | Confirm the selected backup and restore mode | File and directory recovery from supported backups on vStor |
| Application objects | Application-aware protection where granular recovery is supported | A VM image or file restore does not establish application-object recovery |
| Maintenance | Guest installations and application configuration | Proxy infrastructure and hypervisor job configuration |
Combine Approaches Where They Help
A mixed approach makes sense when workloads have different recovery requirements. Use agentless VM protection where its restore options meet the need, then add guest-agent protection for applications that require a more specific recovery workflow.
For example, an application team may need to recover selected application data without rolling back the whole server. Confirm that operation with an application-aware backup and a restore test. Maintain VM protection separately if full-machine recovery is also required.
In DPX VMware jobs, the Include VMs with a DPX client installed option controls whether those guests are included in agentless backup. Make that choice deliberately and account for the capacity and schedules of both backup types.
Instant recovery is a separate recovery capability. DPX documents Rapid Return to Production for temporary VMware VMs created from either block-backup virtualization or agentless Instant VM Restore. Each workflow has its own infrastructure and licensing requirements; combining backup approaches is not a prerequisite.
Choose Around Your Recovery Objectives
Before choosing an approach, agree on the recovery operations your team must complete:
- Identify which workloads need a whole-VM restore and which need file or application-level recovery.
- Set the recovery point objective (RPO) for acceptable data loss and the recovery time objective (RTO) for acceptable downtime.
- Verify support for the hypervisor, guest systems and application versions you run.
- Time representative restores, including an application restart, and check that the recovered data is usable.
- Compare the full operating cost, including backup infrastructure and ongoing administration.
Use the measured results to choose protection for each workload. Agentless backup can reduce guest maintenance while retaining useful recovery options. Add guest agents where the application requirements justify the work.
Explore DPX modern hypervisor protection and the dedicated guides for VMware, Hyper-V and Proxmox VE for platform-specific options. Our VMware backup options article covers related approaches.
Request a DPX demo to review your workload requirements and the recovery workflows your team needs to test.
