MediaAgent Overview

MediaAgents are the multifunction workhorses of a Commvault^® software environment. They facilitate the transfer of data from source to destination, hosts the deduplication database, metadata indexes, and run analytic engines.

For MediaAgent resource requirements and guidelines, refer to the Commvault Online Documentation.

MediaAgents responsibilities include the following functions:

• Data Mover – moves data during data protection, data recovery, auxiliary copy, and content indexing jobs.
• Deduplication Database (DDB) – hosts one or more deduplication databases on high speed solid state or PCI storage.
• Metadata indexes – hosts both V1 and V2 indexes on high speed dedicated disks.
• Analytics – runs various analytics engines including data analytics, log monitoring, web analytics, and the Exchange index for the new Exchange Mailbox agent.

Data Mover Role

The MediaAgent is the high-performance data mover that transmits data from source to destination, such as from a client to a library during data protection operations or vice-versa during data recovery. They are used during auxiliary copy jobs when data is copied from a source library to a destination library. The MediaAgent software can be installed on most operating systems in physical, virtual, and clustered environments. Note that all tasks are coordinated by the CommServe^® server.

MediaAgent and Data Movement

There is a basic rule that all data must travel through a MediaAgent to reach its destination. One exception to this rule is when conducting Network Data Management Protocol (NDMP) dumps directly to tape media. In this case, the MediaAgent is used to execute the NDMP dump and no data travels through the MediaAgent. This rule is important to note as it affects MediaAgent placement.

Since all data moving to/from protected storage must move through a MediaAgent, resource provisioning for MediaAgent hosts (e.g., CPU, memory, and bandwidth) must be adequate for both the volume and the concurrency of data movement you expect it to handle.

MediaAgent Device Control

A MediaAgent provides device control over media changers and removable media devices - and writers to disk devices. This control defines the path upon which data moves to/from protected storage. In addition to normal device integrity checks, the MediaAgent can validate the integrity of data stored on the media during a recovery operation and validate the integrity of the data on the network during a data protection operation.

In the scenario where the MediaAgent component is co-located on the same host as the client agent, the exchange of data is contained within the host. This is called a SAN MediaAgent configuration, or sometimes referred to as LAN-free backups, and has its advantages of keeping data off potentially slower TCP/IP networks by using local higher performance transmission devices (e.g., Fibre Channel, SCSI, etc.). On the other hand, a MediaAgent component located on a host by itself can provide dedicated resources and facilitate exchange of data over longer distances using TCP/IP (e.g., LAN, WAN, etc.).

MediaAgent Hosting Functions

The MediaAgent component also achieves additional functions other than moving data. First, the MediaAgent hosts the index directory. Every protection jobs allowing granular recovery must be indexed. The MediaAgent oversees indexing the jobs and keeping the indexing information in the index directory. If Commvault^® deduplication is enabled on a disk or a cloud library, the MediaAgent also hosts the deduplication database containing the deduplication information. Finally, if Data Analytics is in use, it requires the Analytics Engine to be installed on the MediaAgent.

MediaAgent data movement overview

Deduplication Database

The Deduplication Database (DDB) maintains all signature records for a deduplication engine. During data protection operations, signatures are generated on data blocks and sent to the DDB to determine if data blocks are duplicate or unique. During data aging operations, the DDB is used to decrement signature counters for blocks from aged jobs and subsequently prune signatures, and block records when the signature counter reaches zero. For these reasons, it is critical that the DDB is located on high performance, locally attached solid state or PCI storage technology.

Metadata Indexes

Commvault^® software uses a distributed indexing structure that provides for enterprise level scalability and automated index management. This works by using the CommServe^® database to only retain job-based metadata such as chunk information, which keeps the database relatively small. Detailed index information, such as details of protected objects is kept on the MediaAgent. The index location can maintain both V1 and V2 indexes. Ensure the index location is on high speed dedicated disks.

Analytics

One or more analytics engines can be installed on a MediaAgent. The following provides a high-level overview of the commonly used analytics engines:

• Data analytics – provides a view into unstructured data within an environment. Some capabilities include:
  • identifying old files and emails
  • identifying multiple copies of large files
  • removing unauthorized file types
• Log monitoring – identifies and monitors any logs on client systems. The monitoring process is used to identify specific log entries and set filters based on criteria defined within a monitoring policy.
• Exchange index engine – maintains V2 metadata indexing information for the new Exchange Mailbox Agent. It is recommended when using the Exchange index server that no other analytic engines are installed on the MediaAgent hosting the index.

Physical vs. Virtual MediaAgent

Commvault recommends using physical MediaAgents to protect physical and virtual data. The advantages for using a physical MediaAgent are: better performance, more versatility as a multi-purposed data mover (protect VMs and physical data), and resiliency. If using a tape library, presenting it to a virtualized MediaAgent adds an additional layer of complexity for configuration and troubleshooting (should an issue arise). A MediaAgent can be virtualized if all performance requirements including CPU, RAM, index directory location and deduplication database location are being met.

Tip: Remote Site MediaAgents

You need to protect a smaller remote site and want to keep a local copy of data for quick restore. However, you are concerned about hardware costs for a MediaAgent.

Solution: Virtualize the remote site MediaAgent and keep a shorter retention for the local copy, producing a smaller footprint. Then replicate the data using DASH Copy to the main data center physical MediaAgent where it can be kept for a longer retention.