For most organisations, Microsoft 365 storage costs don’t spike overnight – they creep up quietly. This steady expansion is often accepted as an unavoidable side effect of collaboration in the cloud.
In reality, however, storage growth is usually driven by a handful of factors that actively inflate consumption over time.
Understanding these factors is the first step towards controlling costs and improving governance.
Here are four of the most common that we encounter as Microsoft cloud storage specialists.
- Versioning Bloat
Version history is an extremely useful tool for collaboration. It enables teams to track changes, collaborate safely on shared documents, and restore earlier versions when needed.
The challenge is that version limits are often inherited from default settings and rarely reviewed. As a result, SharePoint libraries can accumulate dozens – if not hundreds – of versions of the same file.
On its own, that might not seem like a major problem. But multiply it across thousands of documents and the storage impact quickly becomes significant.
Optimising version policies doesn’t mean removing version history. It simply means aligning version limits with real collaboration needs.
- ROT
Almost every organisation has a hidden layer of what’s commonly known as ROT – redundant, obsolete, and trivial data.
Think of it as the digital equivalent of a storage cupboard that hasn’t been cleared out for years. Old project folders, duplicate documents, outdated drafts, and files that no longer serve any operational or compliance purpose slowly accumulate in the background.
Over time, this clutter begins to crowd out the information that actually matters. Search results become noisier and less accurate, governance becomes more complicated, and the volume of content that must be reviewed during audits or eDiscovery exercises grows unnecessarily.
Reducing ROT means making deliberate decisions about what information still holds value and what no longer needs to occupy space in your environment.
This is also where labelling becomes valuable. Classification and sensitivity labels give your data context – making it far easier to identify what holds ongoing business or compliance value, and what can be confidently retired. Without that context, all data tends to be treated the same, which leads to over-retention, unnecessary backups, and rising storage costs.
- Cloud Sprawl
One of the great strengths of Microsoft 365 is how easy it is to create new collaboration spaces. Teams, SharePoint sites, channels, and document libraries can all be spun up in minutes.
But that convenience comes with a trade-off.
Without clear ownership or lifecycle controls, collaboration spaces tend to multiply quickly. New Teams are created for projects, departments, and initiatives, while older ones are rarely archived or retired.
Over time, organisations are left with a sprawling environment of inactive workspaces, duplicated content, and inconsistent document structures.
Beyond the storage impact, this fragmentation also makes governance harder. Permissions become more difficult to manage, policies are applied inconsistently, and users often struggle to find the information they actually need.
Bringing collaboration environments under control isn’t about limiting productivity. It’s about introducing sensible lifecycle management, so workspaces are created intentionally and retired once their purpose has been fulfilled.
- Over-Retention
Retention policies play an essential role in compliance and data protection. They ensure important information is preserved for legal, regulatory, or operational reasons.
But in many organisations, retention settings are applied once and then left untouched – often with the default being “keep everything for as long as possible”.
Over time, this “just in case” approach can quietly inflate storage volumes. Data that no longer holds business or regulatory value continues to accumulate, increasing storage costs and risk exposure, while expanding the amount of content that must be searched during investigations or eDiscovery requests.
In some cases, retaining data longer than necessary can also introduce regulatory risk. Many data protection frameworks require organisations to dispose of information once it is no longer needed, meaning excessive retention can become a compliance issue in its own right.
The result is an environment where organisations are storing far more information than they actually need.
Addressing over-retention doesn’t mean reducing compliance standards. It means aligning retention policies with real regulatory obligations and business value, while enabling defensible deletion when information has reached the end of its lifecycle.
- Migration Legacy
Migrations are another quiet contributor to storage growth. When organisations move content into Microsoft 365 – whether from on-premises file shares, legacy SharePoint environments, or other cloud platforms – there’s often pressure to migrate everything to avoid disruption.
The result is that years of accumulated content, including ROT and outdated workspaces, are simply transplanted into the new environment. Storage volumes grow overnight, and many of the issues the migration was meant to solve are carried across with the data.
Approaching migrations with a clear view of what actually needs to move – and applying governance and labelling before the migration, not after – helps ensure storage growth doesn’t simply continue from where it left off.
The Compounding Effect
Individually, each of these issues is relatively manageable. The trouble is: they rarely occur in isolation.
An organisation might be storing years of outdated project files within inactive SharePoint sites, each containing dozens of historical document versions – all preserved by broad retention policies and, in many cases, inherited from past migrations that brought legacy content across wholesale..
Over time, these factors compound. Storage volumes grow, governance becomes more complex, and the effort required to manage, search, and secure information increases accordingly.
Bringing Storage Growth Back Under Control
Storage optimisation isn’t about deleting data indiscriminately. It’s about making deliberate decisions about what information to keep, protect, and invest in – ensuring that storage growth remains intentional, controlled, and aligned with business value.
Once you understand what’s driving storage growth in your environment, you’re in a far stronger position to bring it back under control.
In the next article in this series, we’ll explore how governance and information lifecycle management provide the foundation for doing exactly that – helping organisations address these cost drivers in a structured, sustainable way.