Agent and Agentless Backup Comparision

Recently, the adoption of virtual machines as an integral part of the modern enterprise IT framework has been on the rise. Some organizations now depend on virtualization, and virtual machines manage their databases, business applications, and containerized workloads. These business applications produce significant amounts of data that must not be handled carelessly. This data must be protected. Considering the uniqueness of this business space, customary data protection and backup strategies may not be sufficient to protect this data effectively. At this point, virtual machine backup software becomes important.

An essential feature of virtual machine backup software is its ability to save a copy of your virtual machine files that can be recovered if there’s a breach or downtime. Also, this backup copies the virtual machine configurations so that users can restore the entire backup if things go sideways or if there’s a need to replicate the same environment to test something. Serverwatch opines that the best backup strategy must possess the ability to deliver the most efficient data protection for users’ data.

Should backups be handled completely by virtual machines without the intervention of an agent, or should agents monitor backup processes? This has been a concern for managed service providers who have to determine which approach best suits their clients. Several reasons make this decision an essential one.

To aid comprehension, an agent, in this context, is a small application that is installed on a server to perform a specific task. When backup situations arise, an agent will bolster some applications on that server. Each agent has a specific function assigned to it. Agentless backup is a little confusing. The fact that it is agentless doesn’t mean there’s no agent involved. It has just one, which functions on a specific machine to back up the whole work.

Choosing between agent-based or agentless backups bolsters the primary aim of data protection for business continuity and disaster recovery. Nowadays, a physical server usually hosts multiple virtual machines, while the scalability of virtual machines (VM) facilitates easy transfer within on-premises and cloud space. As a result, procuring and maintaining a unique backup agent for a specific physical and virtual server (agent-based) might be expensive compared to using just a single to manage and backup several VMs (agentless).

Agent-Based Backup

As stated earlier, an agent-based backup requires installing a small application (the agent) on a server to carry out certain tasks. Agent-based backup is useful for products requiring users to install a lightweight rendition of software on each machine they intend to protect. The agent software resides at the kernel level in a secured system. This way, it can effectively detect block-level changes on the machine.

Furthermore, agent-based backups do not require scanning the entire file system to ascertain changes for gradual backups. This makes it more efficient compared to agentless backups for physical machines. Local computing resources must be involved for agent-based backups to perform backups and transfer them to a backup location. As a result, the backup process can affect application performance if the secured server does not possess the computing power that is needed to perform backups, considering the production workload.

Additionally, when system administrators are working in a mixed environment that entails both physical and virtualized servers, agent-based backup is usually required for physical servers. At this point, organizations can select either image-based or non-image agent-based backup.

  • Image-based Backup

This type of agent-based backup takes a snapshot of the entirety of a server’s drives and storage, mitigating the need to reinstall the operating system and recover files that are needed to replicate the previous system. The implication of this is a quick and complete restore devoid of the risks of misplacing important files, which has a possibility of occurring in a non-image-based backup that only operates at the file level.

Moreover, modern image-based backup systems provide detailed file restoration benefits. They can also establish gradual backups by saving only those aspects of the server that were altered by the previous backup.

  • Non-image-based Backup

Non-image-based backup utilizes agent-based backup systems for the recovery of files that have been misplaced, corrupted, or deleted. This type of agent-based backup can not recover overall systems. Nevertheless, it can perform very detailed file recovery.

Pros of Agent-based Backup

  • Very Reliable

Agent-based backups are widely known for their reliability because they possess significant control over the host system. Since agents are positioned at the kernel level, they provide more direct access to data changes in the disc sectors. Consequently, users are provided with faster and more reliable backups.

Owing to the tighter integration with Microsoft’s volume shadow copy service, agent-based backups can establish application-consistent backups.

  • Preferable for Highly Transactional Virtual Machines

Agents are beneficial for highly transactional virtual machines with a database that entails entities like Structured Query Language or exchange. Since the volume shadow service framework can interrupt these transactions at a snapshot, there’s a chance of making errors. Also, since agent-based backups depend on computing resources present on the machine that’s being backed up, the processing speed of various stages is improved.

Cons of Agent-based Backup

  • Higher Cost of Setup and Maintenance

Generally, licensing for agent-based solutions might vary from agentless backup solutions. Physical and virtual machines all require their specific agent, which is why most vendors need a license for each.

  • Possible Downtimes and Maintenance Issues.

Owing to the fact that administrators must reboot systems to install an agent, they cause installation downtime and require time to be active, especially in large networks.

Agentless Backup

As the name implies, agentless backup rules out the need to install agents on secured servers, making it a relatively more straightforward strategy to deploy and monitor. This is essential in virtual environments that host multiple production machines. Agentless backup allows virtual machines to be utilized so easily that they can become unprotected if users decide to switch to agent-based backup because the backup agents never get installed. When organizations decide to adopt agentless backup, issues are mitigated since the agent’s intelligence is centralized from a particular origin and can be set up on a network that spans multiple environments.

Another aspect that gives agentless backup an edge is the virtual machine infrastructure. According to Datto, efficient agentless backup software utilizes the Changed Block Tracking (CBT) incorporated with the hypervisor. This CBT pinpoints data blocks that have been altered or are in use. Furthermore, with agentless backup, you derive additional benefits from virtual storage locations that understand how to migrate data from the hypervisor to the data store, devoid of networking traffic.

Hence, agentless backup ensures that users don’t bother themselves with input/output operations per second on the local virtual machine or rely on network bandwidth that would be an appropriate tool for the production processes.

Pros of Agentless Backup

  • Guarantees Application Consistency

Agentless backup is compatible with snapshot technology, which provides a complete point-in-time version of a virtualized server or virtual machine. This snapshot possesses recovery capabilities that ensure the continuous running of applications without losing data. Consequently, managed service providers can seamlessly maintain application consistency that plays a significant role in achieving business continuity goals. Because snapshot data is uncompressed during storage, it can be easily restored.

  • Less Complicated Administration.

Centralized agentless systems permit administrators to oversee every virtual machine, from minute aspects to the entire network. As soon as the backup administrators set aside the network machines to be used and the data that requires backup, the designated data is migrated to the backup location by the network-based agent. This simplifies the entire recovery process.

  • Effective Control.

Policy-dependent management is a common supplement to agentless backup, promoting improved control of backup and recovery processes while simultaneously reducing work time. Some virtualization software delivers integrated support for agentless backup. An example of this software is VMware vSphere’s Storage API for Data Protection. This application programming interface promotes agentless backup, mitigating the need to install additional backup software.

  • Reduced Cost of Setup and Maintenance.

Agentless backup almost always results in lower costs. Agentless backup cuts down the purchase significantly and licenses the cost of having an individual agent-based backup for each virtual machine on that network. Additionally, it minimizes CPU and bandwidth and reduces communication.

Cons of Agentless Backup

  • The environment must be fully virtual.

Agentless backup requires an absolutely virtualized environment. If organizations adopt physical and virtual strategies, they’ll need two backup strategies, one for the physical and the other for the virtual.

  • Limited Support

Presently, agentless backup is not compatible with image-based backups. This implies that the recovery time can be a little longer. This might not pose any significant threat to less critical systems, or I’d think the organization has a longer recovery time objective.

  • Higher Network Usage

Agentless backup denotes higher network usage compared to agent-based configuration. This is because the system is continuously scanning for alterations in your data. When it finds any alteration, it automatically backs it up. All of this happens over the network.

Eventually, the type of backup an organization adopts depends on its IT strategy, how that promotes its productivity, and cost management methods. If you’d like to learn more about Storware Backup and Recovery solution, feel free to contact us!

Paweł Mączka Photo

text written by:

Pawel Maczka, CTO at Storware