Agents, Backup Sets, and Subclients Overview
Commvault® software uses agents to provide application-aware data protection using native Application Program Interfaces (APIs) and scripting methods. An example of API-based data protection is using Windows file system APIs to protect files on a Windows server. An example of scripting is using Oracle's Recovery Manager (RMAN) scripts to protect Oracle databases. The agent communicates directly with the file system or application requiring protection. Within an agent, a backup set is used as a primary container, which manages all data the agent is responsible to protect. Within the backup set, one or more sub-containers, called subclients are used to explicitly define data requiring protection and to define specific rules for how the data is protected.
Agent, backup set, and subclient high-level concept 
Agents
Commvault® software provides agents for all major file system and applications. Agent support includes traditional streaming backups, built-in content-aware deduplication, Commvault OnePass® archiving, block-level protection, and hardware snapshot capabilities. It is important to note that these capabilities are inherent in the code and can be enabled within the agent.
Commvault agents are categorized using the following general principles:
- Granular agents including file and mailbox agents
- Database agents
- Hypervisor agents
It is beyond the scope of this document to provide detailed information on all agent support.
File System agents
File system agents provide the fundamental data protection strategy in all data centers. File agents are supported for all major operating systems and include inherent file system capabilities based on the operating system being protected. An example is the ability to use Volume Shadow Services (VSS) to quiesce Windows operating systems.
Application agents
Application agents use application consistent point-in-time protection for application databases. Granular application protection for Exchange, SharePoint, and Lotus Notes provides flexible data protection strategies and simplified recovery methods.
Hypervisor agents
The Virtual Server Agent (VSA) provides complete virtual machine (VM) protection and granular recovery of virtual machine data without the need to install traditional agents within a VM. Based on APIs provided by the hypervisor, different protection and recovery capabilities are possible.
Commvault OnePass® Archiving
Archiving removes infrequently accessed data from production storage. This reduces backup and recovery windows and provides a greater return on investment by reducing production storage footprints. File system data, Network Attached Storage (NAS) data, Exchange mailbox, virtual machines and some database applications support Commvault OnePass® archiving.
IntelliSnap® Snapshot Management
IntelliSnap® technology integrates regular protection methods with hardware-based snapshot technologies to coordinate and manage disk snapshots. This integration allows for application-aware snapshots to be conducted for file systems, applications, and virtual environments.
Deploying Agents
Deploying agents can be achieved in several ways:
Available agent deployment methods:
- Push install
- Interactive install
- Custom package
Agent deployment best practices:
- If DNS names are used, ensure the DNS is properly resolving the name forward and reverse.
- If deploying an agent on a remote site, consider using a remote software cache or transfer a custom package.
- If the client is behind a firewall blocking ports, set network configurations to tunnel communication in a port.
Push Install
From the Tools menu | Click Add/Remove Software | Install Software
The CommCell® console is used to push the Commvault® software to clients. The following specific ports are used to achieve the install:
- Commvault base services – Ports 8400 and 8401 are used
- Linux – port 22 is required
- Windows — ports 135, 139, 445 are required
Push installation
Interactive Install
It is possible to download the desired packages on a client machine by using the download bootstrapper. Once downloaded, start the installation by executing Setup.exe.
Interactive installation 
Custom Package
A custom package is a lightweight agent package created by the Commvault administrator. A typical agent installation requires many questions to be answered. The custom package has all these questions pre-answered. It also is useful to run silent installations. If an enterprise level deployment solution is in place, such as Microsoft® SCCM, it can be leveraged to silently push the package to multiple machines.
Creation a custom package
Agent Requirements
It is important when deploying agents, to validate requirements. Prerequisites differ from one type to another. Even for components that you frequently deploy, always confirm as it may change when a new service pack is released.
Most frequent requirement categories:
- Operating system version
- Application version (for application agents)
- Service account with specific privileges
For more information on requirements, please refer to their respective section on Commvault's online documentation.