# Built-in Fail-Safe Features in HyperScale Reference Architecture

Fail-safe features are built into Commvault software and HyperScale nodes for backup and restore operations. Such fail-safe features includes the following:

- When there is a power loss:

  - If there are no active backups running, the nodes and data can be brought back intact once the power is restored.

  - If the power fails during a backup, the backup will be restarted and the uncommitted data will be re-backed up once the power is restored. This is because, during a backup, the HyperScale node commits backup data as a sequence of chunks. (The chunk size can be either 2GB or 4GB depending on the configuration.)

- The HyperScale nodes run the GlusterFS file system, which by itself has the following built-in, fail-safe mechanisms:

  - Every write is committed only if it meets the minimum quorum write requirements. Quorum requirements are setup when you create the HyperScale Storage Pool and can be setup as follows:

    Standard for 3 Nodes, Disperse Factor 6, Redundancy Factor 2. Withstands loss of 2 drives or 1 node.

    Medium for 6 Nodes, Disperse Factor 6, Redundancy Factor 2. Withstands loss of 2 drives or 2 nodes.

    High for 6 Nodes, Disperse Factor 12, Redundancy Factor 4. Withstands loss of 4 drives or 2 nodes.

  - If the minimum quorum write requirement are not met due to a power loss, the backup/restore operations will fail.

    Once the nodes are restarted, the backup/restore operations will continue from the point of failure.

## Related Topic

HyperScale Reference Architecture Best Practice - Resiliency

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