A two-tier data archiving approach can help free primary storage capacity, reduce expenses from regular data protection, and meet compliance or business requirements for specific data.
A two-tier strategy divides archive data based on the probability of accessing that data. Archive data can be accessed online as one tier and a deep archive as another where access may be more involved.
An online archive has these characteristics:
- Data can be transparently and directly accessed by users or applications without other intervening processes.
- The time to access data is only nominally affected compared with primary storage, with no impact on users and applications.
- Typically NAS is used because the largest amount of archived data is in the form of files. There may also be support for objects depending on systems in use.
- The online archive has support for compliance requirements such as immutability with versioning of files, audit trails of access to data, and regular integrity checking of the data.
- The storage is much less expensive than primary storage.
- Only changed files are replicated for protection.
- Systems have built-in longevity with automatic, transparent migration to another platform. The migration is non-impacting to operations or staff.
A deep archive would have different characteristics than the online archive, including:
- Data moved to the deep archive is not expected to be needed again for any normal processing.
- Access from a deep archive may require greater time than applications than tolerate.
- Data may be stored in the form of objects with metadata about ownership and retention controls in order to permit massive scaling. The storage could be on local systems or in a cloud service.
- Longevity is handled automatically by the systems or service with transparent migrations.
- Compliance features are fully supported including digital data destruction.
- Protection is automatic with geographically separated replicated copies.
There is justification for a two-tier archive. You can gain large savings from moving data not expected to be used again to the lowest costing storage without compromising protection, integrity, or longevity. Economic models show the advantage and the compounding value over time as data is retained and more is added. Development of new systems and software that support object storage for very large scale of items in the archive and transparent migration for longevity are enabling wider usage. For all of these reasons, a two-tier archive is a good fit for a storage strategy.