Tiered Storage & Data Archiving: How It Works

What Is Tiered Storage?

Tiered storage is based on pools of storage across which files are stored and accessed — this could be DAS (Direct Attached Storage), NAS (Network Attached Storage), or SAN (Storage Area Network) running iSCSI or Fibre Channel. Typically, an organisation will run a Tier 1 storage platform offering the fastest access to active data, alongside a larger pool of lower-cost SATA disk and tape for older, less frequently accessed information.

Tier 1 storage is also the most expensive to purchase and maintain — it's this storage that typically demands the biggest share of an organisation's storage budget, which is exactly why it shouldn't be used to store data nobody is actively working with.

Why Data Growth Is Forcing a Rethink

Many organisations are struggling with the sheer volume of data being created, and the challenge of organising and storing it without constantly backing up, copying, moving, and purchasing new capacity. Keeping all data — current and legacy — on spinning disk, then backing all of it up, is unsustainable once volumes reach a certain scale.

Tiered storage gives organisations a way to strategically decide what stays on Tier 1 disk and what moves to lower-cost options such as SATA RAID, cloud storage, tape, or optical — without losing accessibility to that data.

HSM vs. Tiered Storage

The traditional way of archiving data was HSM (Hierarchical Storage Management) — a method that evolved from the mainframe era, where entire areas of data were archived to a device or drive letter. It was the primary approach through the 1990s, but modern tiered storage addresses many of its core limitations.

Policy Rules: What Tiered Storage Can Act On

Once tiered storage is in place, policy rules can be created to automatically manage data based on a wide range of criteria — with actions including:

Active Data Archiving

An Active Data Archive works alongside tiered storage to identify, move, and manage inactive data automatically — without breaking file paths or requiring users to know where a file physically lives. The task many IT managers face is separating current data from historical data; a detailed usage report covering IOPS, ownership, and last-accessed dates is typically the starting point.

Once that data is identified, simple policy rules can move it based on age, file size, user or group, file extension, last accessed or modified date, or project folder — scheduled to run out of hours, entirely transparent to users. When a user does need a file, it's automatically pre-migrated back to primary tiered storage.

Disaster Recovery

More organisations are adopting a DR strategy as part of corporate governance and compliance. A DR strategy might involve a cluster of servers, remote data replication to a DR site, or backup tapes for restoration. An Active Tiered Storage Data Archive helps significantly here, reducing the volume of data that needs to be backed up or replicated to a DR site — meaning DR restores only need to cover the data that's actually on the primary file server.

Aged data can also be automatically replicated to your DR site as part of the same policy-driven process.

Storage Management & Compliance

How organisations control and police the lifecycle of their data is a continually growing problem — many data compliance and corporate governance regulations require information to be retained for a minimum period and then deleted. A tiered storage solution addresses this by creating policy rules based on data type: for example, a newly issued insurance policy might need to remain on primary storage for the first 60 days for accuracy checks, move to SATA after that, and finally migrate to cloud, tape, or optical storage after 120 days for long-term archive — all with minimal human intervention once the rules are in place.

An Active Data Archive combined with tiered storage becomes an essential part of a corporate governance and compliance strategy — categorising and storing data based on its value and usage, while reporting and discovery tools track file movements and flag file types that shouldn't be on the corporate network.

Backing Up vs. Tiering

It's worth being clear on the distinction: backing up data does not move it through the storage tiers. A backup exists purely to ensure data can be restored in the event of a disaster. As data volumes rise and backup windows shrink, backup needs to become more selective rather than a blanket "back up everything" policy — with periodic backups used to retain an archive copy of already-migrated data.

Reduced Costs

Once a tiered storage solution is implemented, the investment typically pays for itself in a relatively short timeframe — freeing up disk space on primary Tier 1 storage, reducing energy costs by moving data to lower-cost platforms, and shrinking the backup window.