Immutable repositories are backup storage locations that prevent unauthorized modifications or deletions of backup data, ensuring its integrity and recoverability. Immutable repositories are essential for protecting backups against ransomware attacks, accidental deletions, or malicious insiders1.

Veeam Backup & Replication supports several types of immutable repositories, such as hardened repositories, immutable object storage repositories, and immutable deduplicating storage appliances2. Among these options, the best configuration for ensuring SLA compliance and providing protection against ransomware is to leverage hardened repositories at both primary and secondary sites, and offload to object storage in a public cloud with immutability enabled.

Hardened repositories are Linux-based repositories that use XFS file system with immutability flag to protect backup files from changes or removals. Hardened repositories can be used as primary or secondary backup targets, and can be combined with Veeam Scale-out Backup Repository to simplify backup management and optimize storage utilization3.

Object storage repositories are cloud-based repositories that use object storage services, such as Amazon S3, Microsoft Azure Blob Storage, or Google Cloud Storage, to store backup data. Object storage repositories can be used as secondary backup targets, and can leverage the immutability feature of the cloud provider to prevent backup data from being overwritten or deleted.

By using hardened repositories at both primary and secondary sites, you can achieve high availability and redundancy for your backup data, as well as fast and reliable restores. By offloading to object storage in a public cloud with immutability enabled, you can achieve long-term retention and compliance, aswell as cost savings and scalability. This configuration also follows the 3-2-1-1 backup rule, which recommends having three copies of data, on two different types of media, with one copy off-site and one copy immutable.

You can find more information about immutable repositories and how to configure them in the following resources:

Immutable Backup Solutions: Linux Hardened Repository

Unstructured Data Backups in Immutable Repositories

Hardened Repository

[Immutability for Object Storage Repositories]

[3-2-1-1 Backup Rule]